1444 User Manual

1. 1444 High Voltage Card

1.1 Introduction 1.1.1 Purpose

This manual is intended to provide instruction regarding the setup

and operation of the Model 1444 High Voltage Card. In addition, it

describes the theory of operation and presents other information

regarding its application.

1.1.2 Unpacking and Inspection

It is recommended that the shipment be thoroughly inspected

immediately upon delivery. All material in the container

should be checked against the enclosed Packing List and

shortages reported promptly. If the shipment is damaged in

any way, please notify the Customer Service Department or the

local field service office. If the damage is due to

mishandling during shipment, you may be requested to assist

in contacting the carrier in filing a damage claim.

1.1.3 Warranty LeCroy warrants its instrument products to operate within

specifications under normal use and service for a period of

one year from the date of shipment. Component products,

replacement parts, and repairs are warranted for 90 days. This

warranty extends only to the original purchaser. Software is

thoroughly tested, but is supplied "as is" with no warranty of

any kind covering detailed performance. Accessory products not

manufactured by LeCroy are covered by the original equipment

manufacturers' warranty only.

In exercising this warranty, LeCroy will repair or, at its

option, replace any product returned to the Customer Service

Department or an authorized service facility within the

warranty period, provided that the warrantor's examination

discloses that the product is defective due to workmanship or

materials and has not been caused by misuse, neglect, accident

or abnormal conditions or operations.

The purchaser is responsible for the transportation and

insurance charges arising from the return of products to the

servicing facility. LeCroy will return all in -- warranty

products with transportation prepaid.

This warranty is in lieu of all other warranties, express or

implied, including but not limited to any implied warranty of

merchantability, fitness, or adequacy for any particular

purpose or use. LeCroy shall not be liable for any special,

incidental, or consequential damages, whether in contract, or

otherwise.

1.1.4 Product Assistance

Answers to questions concerning installation, calibration, and

use of LeCroy equipment are available from the Customer

Services Department, 700 Chestnut Ridge Road, Chestnut Ridge,

New York 10977 -- 6499, (914) 578-6030, or your local field

service office.

1.1.5 Maintenance Agreements

LeCroy offers a selection of customer support services. For

example, Maintenance agreements provide extended warranty that

allows the customer to budget maintenance costs after the

initial warranty has expired. Other services such as

installation, training, on-site repair, and addition of

engineering improvements are available through specific

Supplemental Support Agreements. Please contact the Customer

Service Department or the local field service office for

details.

1.1.6 Documentation Discrepancies

LeCroy is committed to providing state-of-the-art

instrumentation and is continually refining and improving the

performance of its products. While physical modifications can

be implemented quite rapidly, the corrected documentation

frequently requires more time to produce. Consequently, this

manual may not agree in every detail with the accompanying

product and the schematics in the Service Documentation. There

may be small discrepancies in the values of components for the

purposes of pulse shape, timing, offset, etc., and,

occasionally, minor logic changes. Where any such

inconsistencies exist, please be assured that the unit is

correct and incorporates the most up -- to -- date circuitry.

1.1.7 Software Licensing Agreement

Software products are licensed for a single machine. Under

this license you may:

* Copy the software for backup or modification purposes in

support of your use of the software on a single machine.

* Modify the software and/or merge it into another program

for your use on a single machine.

* Transfer the software and the license to another party if

the other party accepts the terms of this agreement and

you relinquish all copies, whether in printed or machine

readable form, including all modified or merged versions.

1.1.8 Service Procedure

Products requiring maintenance should be returned to the

Customer Service Department or authorized service facility.

If under warranty, LeCroy will repair or replace the product

at no charge. The purchaser is only responsible for the

transportation charges arising from return of the goods to

the service facility. For all LeCroy products in need of

repair after the warranty period, the customer must provide a

Purchase Order Number before any inoperative equipment can be

repaired or replaced. The customer will be billed for the

parts and labor for the repair as well as for shipping. All

products returned for repair should be identified by the model

and serial numbers and include a description of the defect or

failure, name and phone number of the user. In the case of

products returned, a Return Authorization Number is required

and may be obtained by contacting the Customer Service

Department in your area. New York Corporate Headquarters

(914) 578-6030 or (914) 425-2000, New Hampshire (603)

627 -- 6303, Virginia (703) 368 -- 1033, New Mexico (505)

293 -- 8100, California (415) 463 -- 2600

1.2 Product Description

1.2.1 Introduction

The 1444 High Voltage plug-in card supplies eight

programmable high voltage outputs when used in a 1440 high

voltage system. As many as 16 of these high voltage cards can

be installed in a 1449 mainframe, providing up to 128 high

voltage outputs. Each channel can supply up to 5.6 kV with

provisions for voltage limits, voltage and current

monitoring, AC and DC current trips and inter-channel trip

protection. Both a positive and a negative voltage version of

the 1444 High Voltage card is available, identified as 1444P

and 1444N respectively.

Any number of 1444 HV cards can be used in the 1440 system in

conjunction with 1443 HV cards, thus allowing the addition of

higher voltage channels to an existing system.

1.2.2 Specifications

The maximum output voltage of the 1444 HV card has been

increased over the 1443 HV card to 5.6 kV. Each channel is

independently programmable from 0 to 5.6 kilovolts in 0.5

volt steps.

Each channel can deliver a maximum 1.0 milliamperes. This

current can be monitored at the front panel and through the

system controller, either a 1445 or a 1445A.

The AC current for each channel is monitored on the 1444 HV

card itself. Four programmable AC current trip values (one

for each pair of channels) are supported. The AC current is

monitored at frequencies between 3 and 160 Hz. Sensitivity is

programmable from 15 nA to 4 u,A.

Monitor connections for voltage, current, and trip are

provided for each channel. Channel trips may be inter

-- connected to cause channels to trip off as a group.

Clamp to +5V indicates a trip has occurred. External user

logic may also be used.

Ramp rates are programmable over the range 300 to 1500 V/s on

a channel by channel basis. All voltage changes, both up,

down, and trip off, will occur at the programmed rate.

1.2.3 Controls and Connectors

All information and control is available and normally

obtained through the 1440 system controller, either a 1445

or a 1445A, but the 1444 HV card includes four external

monitors per channel. Each channel has a 10 pin header and

potentiometer. The header provides five signals on the odd

numbered pins (right column) with associated grounds on the

even numbered pins. This header allows one to monitor the

high voltage, the current, the voltage limit, and trip status

of each channel with external hardware. The TRIP connections

can also be used to induce trips.

The high voltage output of each channel is monitored in two

ways. On demand from the 1440 system controller the 1444 HV

card gates the buffered output of a channel's voltage divider

onto the system backplane. This DC level is digitized in the

controller and available to the user. At the front panel

header Vmon is the buffered output of this voltage divider.

It provides a voltage monitor at 1 mV/V and is NOT INTENDED

FOR CALIBRATION USE.

The DC current drawn by each channel is monitored in two

ways. Each channel on a 1444 HV card generates a voltage

level proportional to the DC current being delivered to the

output. This voltage level is sent to the system controller

on demand and is also available at the front panel header,

Imon, in units of 1 mV/uA.

The signal Vlim presents the high voltage limit setting at

the header in the same units as Vmon. The voltage limit is

adjusted with the potentiometer directly above the header

(one per channel). This voltage limit is provided in place

of the crate wide high voltage limit generated by the 1441

power supply. The crate wide limits are not used by the 1444

HV card.

The AC current output of each channel is monitored above 3

Hz. If the current exceeds the programmed limit that single

channel is tripped off, the TRIP signal is asserted (NATL

high), and the fault LED is illuminated. During the next

update cycle (less than 512 ps), the demand voltage will be

set to zero and the output voltage will begin to ramp down to

zero at the programmed rate. Channels tripped off due to over

current must explicitly be reset with the controller. All

channels on a card are reset simultaneously.

TRIP connections on the front panel header allow the

interconnection of channels to form a single AC current trip

circuit. Thus if one of a set of inter-connected channels

exceeds its AC current limit the entire set of channels will

be ramped to zero volts. The two TRIP connections on each

header are identical and intended to be used in a daisy

chain. Up to 100 channels may be connected in this way.

Larger groups may be formed with external logic. The fault

LED of channels suppressed by the TRIP input are not lit.

The TRIP signal also can be used to detect or simulate a

trip. Channels with the TRIP signal asserted (clamp to +5 V)

will ramp to zero. When the TRIP signal is removed

(deasserted) from the front panel, the channel output will

ramp back up to its demand value, unless of course it has

been tripped. Only cards with a channel asserting TRIP

require a reset.

The demand voltage is the digital number which produces the

desired output voltage. This digital value can only be

supplied to the 1444 HV card by the 1440 system controller.

The digital value is converted by the 14 bit DAC and stored

on a capacitor. The controller updates each channel in the

1440 system once every 512 p.s.

The rate at which the output voltage changes is programmable

over the range 300 to 1,500 volts per second. This ramp rate

is used any time the voltage is changed, except when the 31

volt power is turned off either by the controller or the

operator, or a failure of the power supply. In this case, the

rate of change is determined by the load. Highly capacitive

loads may also limit the ramping rates.

1.2.4 Commands

The user's interface to the 1444 HV card is through the 1440

system controller, either the 1445 or the 1445A. Each

controller offers various levels of support for the 1444 HV

card. Consult the user's manual for your controller for

details. The following description refers to commands issued

by the controller to the 1444 HV cards. This information is

useful for a general understanding of the 1440 system as a

whole and the 1444 HV card in particular. First time users

may wish skip to the Installation section.

The 1444 HV card receives commands over the data bus of the

1440 system. Approximately 2,000 times a second the

controller of the 1440 system transmits a digital word to

each of the 16 ports, numbered 0 to 15, on the 1444 HV card.

A 14 bit Digitalto Analog converter (DAC) on the 1444 HV card

is used to generate a reference voltage for each port.

The first eight of these 16 ports control the high voltage output of the eight channels, similar to the 1443 HV card.

The digital data sent to these ports are converted to

reference voltages used by the high voltage generation

circuit. Normally, the 14-bit DAC is calibrated to output

reference voltages corresponding to the range 0 to 8191.5

volts in 1/2 volt steps. The actual output is limited to

5600 volts. The calibration of all channels on the card will

be degraded while any channel is programmed in excess of this

limit.

Port 8 selects the ramp rate. This is the rate at which the

output high voltage on this card will be changed. Again any

14 -- bit number is acceptable. Values corresponding to the

voltages 0 to 8195.5 volts will select ramp rates between 300

and 1500 volts per second. The actual ramp rate will vary

about ten percent from channel to channel.

Port 9 is used to control and reset the AC and DC current

trip system for the entire board. Before an over current

condition can cause a trip, the system must be enabled. This

is done with a write of the value corresponding to 4095 volts

to port 9. After the over current condition has been detected

and the voltage has been tripped off, a reset is required to

restart the 1444. A reset is accomplished by writing zero to

port 9 and then enabling the trip system as before. In

version 2.0 of the 1445 firmware, the CLEAR command performs

this function of reset and trip enable.

Port 10 is not used.

A write operation to ports 12 through 15 sets the AC current

trip value. This value is roughly proportional to the AC

current at which a channel will be tripped off, i. e. large

values provide the least sensitivity. Any 14-bit value is

acceptable (the 1445 controller will only send 12 bits) but

the desired value may require experimentation.

Port 11 is used to set the DC current trip level. This value

is calibrated with 1.024 mA as full scale. The resolution is

2 uA.

The following table summarizes the function of the 16 ports

as data is written to the 1444.

Port Operation

0 Channel 0 Set Voltage

1 Channel 1 Set Voltage

2 Channel 2 Set Voltage

3 Channel 3 Set Voltage

4 Channel 4 Set Voltage

5 Channel 5 Set Voltage

6 Channel 6 Set Voltage

7 Channel 7 Set Voltage

8 Set ramp rate

9 Reset all channels tripped

10 (unused)

11 DC current Limit

12 AC current trip limit Channels 0 and 1

13 AC current trip limit Channels 2 and 3

14 AC current trip limit Channels 4 and 5

15 AC current trip limit Channels 6 and 7

The 1445A controller and the 1445 controller with version 2

firmware, identifies the 1444 card in a system and properly

initializes all the ports as described. When the 1444 is

first detected, the AC and DC current trips are set to

minimum sensitivity, the ramp rate is set to the maximum

rate, and the trips are enabled. These controllers will not

allow operations without trips enabled. When the controller

identifies a 1444 card in a slot where at 1444 was found

during the previous power up cycle, all the trip and ramp

settings are preserved.

The 1445 controller with version 1 firmware cannot identify

a 1444 card and these features must be initialize manually.

Due to this and other difficulties, the 1445 controller with

version 1 firmware is not recommended.

The 1440 system controller can also read data from sixteen

ports on the 1444 HV card. On command from the system

controller each port gates an analog voltage on the backplane

of the 1440 system to be digitized by the ADC in the

controller (12 bits in the 1445 and 15 bits in the 1445A).

Ports zero through seven directly measure the high voltage

output of their respective channels with a precision voltage

divider. The output of this divider is the same used for

controlling the output voltage. If the voltage measured by

the controller deviates substantially from the demand voltage

(10 volts), the system is malfunctioning.

Ports eight through fifteen provide a measurement of the

current being drawn by each channel.

The following table summarizes the function of the 16 ports

as data is read from them.

Port Operation

0 Channel 0 Set Voltage

1 Channel 1 Set Voltage

2 Channel 2 Set Voltage

3 Channel 3 Set Voltage

4 Channel 4 Set Voltage

5 Channel 5 Set Voltage

6 Channel 6 Set Voltage

7 Channel 7 Set Voltage

8 Channel 0 DC current

9 Channel 1 DC current

10 Channel 2 DC current

11 Channel 3 DC current

12 Channel 4 DC current

13 Channel 5 DC current

14 Channel 6 DC current

15 Channel 7 DC current

1.3 Installation

The 1444 HV card is intended to be used in a 1440 system. The 1440

system consists one or more 1449 or 1449E mainframes. Each mainframe

contains either a 14l5 or 1445A controller, a 1441 power supply and

control unit, one or two 1442 power supply units, and one to sixteen

1443 or 1444 high voltage cards in any combination. Each 1443 HV card

adds 16 channels of 2.5 kilovolts and each 1444 HV card adds eight

channels of 5.6 kilovolts to the system.

With the power off, the 1444 HV card is inserted into one of the 16

slots in the back side of the 1449 mainframe. Because of the large

card size, care must be used to insure that the correct pair of card

guides have been engaged. The edge connector on the card should mate

with the bus connector with only modest pressure. Both the upper and

lower thumb screws should be engaged and tightened. These screws

should neither be required nor used to force the card into position.

Take note of slot number, as this is used in addressing the 1444 HV

card.

At this point the 1444 high voltage card is ready for operation.

Consult the appropriate sections for any other hardware installation

which may be required.

Further installation may include any or all of the following:

Adjustment of the voltage limit for each channel (1 mV/V) with power

on and high voltage off. With the power off, connect the high voltage

equipment to desired channels. Make any TRIP, current monitoring

(Imon), or voltage monitoring (Vmon) front panel connections.

1.4 Operating Instructions

Operation requires giving commands to the system controller, either

a 1445 or a 1445A. Consult the manual for your controller for

complete details of commands. Because the 1444 HV card is not

recognized as different from a 1443 HV card by early versions of the

1445 controller firmware, some accommodation by the user may be

required. Later versions (version 2.0 and later) of the 1445 firmware

support the 1444 to a large degree but not as completely as the 1445A.

The following sections show examples of 1444 operation with a 1445

controller and the two major versions of the firmware.

1.5 Theory of Operation

The following is a description of the proper function of both the

1444N and the 1444P high voltage cards. As each circuit is described,

the references to schematics are shown in parentheses. In general the

references are the same for both schematics and exceptions are noted.

Figure B -- 1 shows the parts relevant to channel zero. Since channels

one through seven are nearly identical to channel zero, these pages of

the schematic are not included in the appendix. Reference numbers are

such that the hundreds digit minus one is the channel number, thus U101

is a part in channel zero and U701 is the corresponding part in channel

six. Parts not specific to a single channel have reference numbers

below 100.

High voltage generation is accomplished by delivering a fixed

frequency, pulse width modulated current to the primary of a resonant

transformer (a4). The transformer has a 43:1 turns ratio. The output

of the secondary is rectified and twice doubled (b4). Finally a

multistage filter (c4) conditions the output.

The output voltage is monitored with a 100 M/100 K volt;age divider,

R100 (c4). The voltage divider is extended with the resistors R113

and R119. The network CR107, Clxx, and R112 provide partial

compensation for the voltage coefficient of the hybrid voltage

divider. The voltage coefficient is less the 5 ppm/Volt.

The center of the voltage divider (c4) is compared to the control

voltage, VCONT (a2), by the error amplifier, U103. As the output of

U103 decreases (approaches zero), the power delivered to the output

is increased. Since the feedback voltage is driven to match demand

voltage, VCONT, the voltage monitors will not be affected by

adjustments to R113 (c3). This adjustment calibrates the high voltage

output.

The TL082 U103 (b3) is the error amplifier. The output of this

amplifier controls how much power is delivered to the transformer and

thus adjusts the high voltage output. U102 (b3) is a LM311 voltage

comparator. As more power is required, the output of the error

amplifier will approach zero volts. RAMP is a triangular shaped

waveform such that a longer pulse delivered to the switch transistor,

Q100, as the output of U103 decreases. Q100 modulates the current to

the transformer. Four separate RAMP signals are used to level the

power requirements of the eight channels.

The demand or control voltage, VCONT, is stored on the capacitor C117

(a2). The voltage across this capacitor is limited by the voltage limit

circuit (ab2) which is adjustable from the front panel with R105 (c2).

The range and units of Vlim are the same as Vmon.

The op-amp U100 (cd3) is a voltage follower, driving both the front

panel monitor J100 (e2) and VMON. Note that the voltage divider, formed

by R101 and R100 (d23), provides an approximate calibration of 1 mV/V

at J100.

The output current is monitored by the OP07, U101, (d3). The left end

of R116 is a virtual ground. The ground potential is maintained by the

op-amp driving sufficient current through R116, thus the voltage drop

across R116 is a measure of the current. This voltage is distributed

several places including the front header, J100. R102 and R103 (42)

form a voltage divider to calibrate the output to 1 mV/uA.

The AC trip level is determined by the signal VTRIP (cl). The time

constant for an AC trip can be selected with the jumper J101 (c2).

When an AC trip occurs, the JK flip-flop (al) is cleared. This causes

both signals TRIP and TRIP_OR to be driven until a reset is received

via TRIPMESET.

If the channel is inter-connected via the TRIP_OR signal, the high

voltage will switch off while the TRIP_OR is driven but cannot be

tripped off, as the flip-flop will not be cleared. High voltage output

will resume as soon as TRIP_OR is no longer asserted.

The current trip is implemented by U104 (c2). The current limit

reference voltage is opposite in sense to the voltage measuring the

output current. When zero is crossed at the input to the op-amp, the

trip flip -- flop is clocked, similar to the AC trip. Figure B -- 2

shows the digital section of the 1444P HV card.

Data for a particular channel in the 1444 HV card is transferred over

the data bus once every 512 us. Each transfer requires four cycles at

2 MHz, transferring four bits (one nibble) per cycle. The data

transferred is presented to the DAC, and the DAC output is transferred

to the correct storage capacitor. Note that for compatibility with

other high voltage cards the bits are transferred in an unusual order.

The first nibble contains the sign bit on DB3* ("*" indicates a low

true signal), and the two least significant bits of the 14 bit demand

voltage. The sign bit is true (low) for positive and false (high) for

a negative value, contrary to some sign conventions. The next three

nibbles appear in descending order of significance and form the

unsigned magnitude of the demand voltage. Note that the sign bit is

not currently checked on the 1444 card, the controller is responsible

for maintaining the correct polarity of the data.

The update cycle begins with the assertion of CSEL* (a4). At this time,

Nibble Controller, U27, (a3) asserts SEL, and holds it for the required

four clock cycles. The signal SEL clocks the channel address from

CA2-CA5 into the ADDRESS_LATCH pal, U24 (e2), gates the data from

DBO* -- DB3* onto the data bus, DATA(0:3) (a3), and enables the upper

and c lower byte registers U30 and U28 respectively. If TRIP_OR is not

set for the current channel (e2), then the next four nibbles of data

are assembled into a 14 bit input word for the DAC, U32 (c3). If the

above conditions are not satisfied, a zero word is presented to the

DAC. This data is latched until the next cycle, 32 us.

If the data being sent is a demand voltage, then output of the DAC is

diverted to the RUN UP/RUN DOWN circuit (c4). U28 (e4) is a

bi-directional analog mux. When enabled, the existing voltage on the

channel's memory capacitor is compared with the output of the DAC. One

or both of the current sources I_RUN_UP and I_RUN_DOWN are used to ramp

the voltage on the capacitor. Note one current source is twice the

other with the opposite sense, thus the selection of both causes

charging at the same rate as one but in the opposite direction. Also

note that UP and DOWN refer to the voltage direction; thus on the 1444N

HV card UP is towards ground and on the 1444P HV card UP is toward high

voltage output.

If the data being sent refers to one of the other functions of the 1444,

the output of the DAC is sent directly to the analog mux, U25 (e3),

where the voltage across the memory capacitor is set promptly.

Monitoring of voltage and current is done by gating one of the

monitoring voltages (dl,d2) onto the VFB line (a1) of the backplane.

The signal FSEL* initiates a sample and FBO-FB3 selects the channel

and function. Each slot has a unique VFB and FSEL* line. The NEG*, POS*

and ID1* lines are used to identify the type of module in a particular

slot. When addressed with FSEL* the identification lines are asserted,

unless the addressed channel is currently tripped off (not just held

low with the TRIP_OR signal). In this case, the polarity is not

asserted. This allows the controller to identify tripped channels.

Figure is the schematic for the ramp generators, the charging

currents generators and a few miscellaneous circuits.

The RAMP GENERATORS (al) convert the SYNC pulses into the RAMP signals

used by each channel. Thesignals go rapidly positive and ramp back

towards -1.4 volts. The RAMP and the output of the error amplifier

control the pulse width to the transformer.

The run up and run down currents (e3) are generated with a series of

current mirrors. The signal VIE (c2) establishes the initial current

in R51. R55 sets the minimum allowable current in the circuit. The sum

of these currents flow through R50. Now the same voltage drop appears

across R49 and R51. The current through R57 is doubled and changed in

sense when it reaches I_RUN_DOWN.

The circuit at d4 senses the presence of the 31.5 volt power supply,

generating a signal with digital levels. The controller switches this

supply on only during high voltage generation. The signal 30V_ON*

provides an interlock to the digital section. When not asserted (high),

only zero will be presented to the DAC. This interlock can safely be

defeated for diagnostic purposes.

The circuit at d4 and c4 converts the activity of VRESET to digital

logic levels. The output is used to reset tripped channels.

DCLIM (dl) is buffered and inverted to create the current limit

reference voltage for all channels.

1.5.1 Service Hints

The following are a few hints to experienced professionals

on how to approach a non -- working high voltage card. If any

of the problems described here are observed, the cards should

be returned for service by experienced professionals. High

Voltage is dangerous, both to the electronics and engineer. We

DO NOT recommended that any of the following procedures be

done by the customer. Performing any one of these procedures

will void any warranties.

* It is highly recommended to operate a suspect high voltage

card with loads on all channels (5.6 MOhms), especially

after a repair. If a problem with voltage regulation

exists, the card will be unable to generate voltages much

in excess of 5.6 kV.

* If the observed problem is that the actual high voltage

output is more than 10 volts higher than the voltage

indicated by the controller, while other channels on the

card are correct, check for a voltage drop across R117

(figure,c3) on the relevant channel. If there is a voltage

drop, then it is possible that the diodes CR113, CR103 or

the capacitor C126 have been damaged and become resistive.

Each may be cut in place or measured with the board out of

the crate.

* The problem is unknown or after an extensive repair. We

would like to see the board operate without actual high

voltage generation. Normally, when the power to the high

voltage is off the demand data sent to the 1444 HV card is

ignored and zeros are used. To defeat this interlock and

allow the DAC to generate voltage levels, insert U27 with

pin 7 out of the socket. This pin will float low (all

production units use CMOS for UZI), and simulate the

presence of power to the high voltage.

1.6 Calibration Procedures

The following procedures assume that the 1444 card is functioning

correctly and that the operator is familiar with the 1440 system

controller. To complete these procedures the following equipment is

required:

* 1440 High Voltage system with properly calibrated controller

* 1444/1443 extender card with support rail or a 1440 system with

side panel cutout for access to the 1444 card

* 1588A-44 Load Card, 5.6 MOhms, 8 channels

* VT100 type terminal or personal computer with communications

software, and cable, CDHV16-M

* Precision voltmeter, 5 1/2 digits, 0.01% DC accuracy

* Precision voltage divider, 1000:1 Ratio, 0.01% Accuracy

* Oscilloscope, 300 Mhz bandwidth, 2 channel

The first step is to zero the feedback amplifier. Put the 1444 card

in the system and turn the power on, but not the high voltage. Adjust

R31, the third and unlabelled pot near the DAC, until the voltage drop

from U31 pin 2 to U31 pin 12 is zero. This pot can be glyped at this

time.

Next we adjust the offset and gain of the DAC. Turn all the voltage

limits fully clockwise. Program the card for 1, 2, 3, 4 and 5 kV on

channels 0 through 4 respectively and turn on the high voltage. The

worst possible calibration should not generate dangerous overvoltages.

Use the monitor command to observe all channels continuously. Adjust

the offset and gain, R37 and R36 respectively, until the displayed

voltages are correct. The offset and gain pots are labeled as such.

These pots can be glyped at this time.

Program the output voltage to 3500 volts. The controller should read

exactly 3500 volts on all channels. For each channel, adjust Rx20

(column of pots nearest the backplane of the 1440 system) until the

voltage on U101 pin 2 is zero. Use test point two, near the edge

connector for ground. These pots may be glyped at this time.

With the high voltage divider and the voltmeter, adjust the output

voltage of each channel to within 1/2 volt of 3500 volts. The

adjustment is Rx19, the next column of pots.

Finally, we adjust the transformer resonance. With the oscilloscope

observe the waveform on the collector of the TIP31 which is attached to

the heat sink. Take care not to short to the heatsink or the screw

securing the transistor. The waveform should appear as an approximate

sine wave with a negative notch. The center screw of the transformer is

adjusted until the notch begins exactly half way between the maximum

and minimum of the sine wave.

Be aware, the transformer adjustment screw is very fragile, a plastic

screw bonded to ferrite material. If the screw is broken is the entire

assembly must be tapped out and replaced.

2. Examples

2.1 Version 2.0 Firmware

The following is a sample terminal session with the 1445 controller

using version 2.0 and the RS232 interface. Information which appears on

the screen is shown a the typewriter font and text typed by the

operator is underlined.

LeCroy 1440 V2.17

This is the sign on message displayed after power up. The firmware

detects the presence of a newly inserted 1444 HV card in the crate and

sets the ramp rates to the maximum rate and the AC and DC current trips

to the minimum sensitivity.

2> main 2

Note that a prompt appears. By default the controller connects to the

terminal after power up. It is a good idea to specify the desired

mainframe to ensure only one is attached. Note the prompt indicates

which mainframe is attached.

2> sho modules

Slot Module

0 1444N

1 -------

2 -------

3 -------

4 -------

5 -------

6 -------

7 1443N

8 -------

9 -------

10 -------

11 -------

12 -------

13 1443N

14 -------

15 -------

This command displays the contents of the crate. Note that commands

can be abbreviated to two letters, but misspellings are not allowed.

2> read (0,0-7)

Channel Demand Voltage Current ( 0, 0) - 0.0 - 0 0

( 0, 1) - 0.0 - 0 0

( 0, 2) - 0.0 - 0 0

( 0, 3) - 0.0 - 0 0

( 0, 4) - 0.0 - 0 0

( 0, 5) - 0.0 - 0 0

( 0, 6) - 0.0 - 0 0

( 0, 7) - 0.0 - 0 0

A read command shows the state of the specified 1444 HV card.

2> wr -500.5,0,-400,,-500

Specify several demand voltages. Note that there are several new

features used in this command. A zero demand voltage is special and

does not require a minus sign. The loop specified in the previous

command is used until another loop is specified. The last voltage is

repeated until the end of the loop. Finally, a null may be specified by

two consecutive commas, and a null will not alter the demand voltage

of the corresponding channel.

2> re Channel Demand Voltage Current ( 0, 0) - 500.0 - 502 2

( 0, 1) - 0.0 - 0 0

( 0, 2) - 400.0 - 398 3

( 0, 3) - 0.0 - 0 0

( 0, 4) - 500.0 - 496 4

( 0, 5) - 500.0 - 498 3

( 0, 6) - 500.0 * 0 0

( 0, 7) - 500.0 - 498 4

Note that channel six above shows a star in place of the sign. This

is characteristic of a channel which has been tripped by the AC or DC

current limit. A Clear command will reset this and allow the voltage to

ramp up.

Also note that if there is voltage on the output of a tripped channel

the 1445 controller will display this for a 1444N but not for a 1444P.

This is corrected in the new 1445A controller.

Another restriction is the 12 bit limitation of the ADC in the 1445

controller. The LSB of this ADC corresponds to two volts in the output

voltage of the 1444. To compensate, the firmware takes eight

measurements and displays the average of these measurements to the

nearest volt. This is corrected in the 1445A controller.

2.2 Version 1.7 Firmware

The following is a sample terminal session with the 1445 controller

with version 1.7 firmware, over its RS232 port. The allowable syntax is

very complex, and here ice will show only the brief form of a few

commands and describe the results. Consult the controller manual for a

complete description of commands. For this example, we assume a 1444N

has been inserted into slot 1. Note that uppercase characters are

required by version 1.7 firmware.

Version 2.0 firmware is recommended when using 1444 HV cards. Please

skip this section if you have or can obtain version 2.0 firmware for

your 1445 controller.

Version 1.7 f