20-327 Beam Voltage Adjustment

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This post is about how to adjust the 20- 327 2kV beam voltage for the elastic peak.

Click on the link below to go to the .PDF

20-327 beam voltage adjustment

The 20-327 electron gun control is used on the Physical Electronics 610 series scanning auger electron systems.  The 20-327 is also a replacement for the obsolete 18-080 and 18-085 electron gun controls.

20-327 front panel

20-327 front panel

Once you have adjusted your elastic peak for best shape with max counts you will need to adjust your 20-327 R47 for proper alignment of the beam voltage calibration. Please read all of procedure before proceeding.

1)    Place a piece of clean copper in your system, Run an alignment and adjust your Z axis until you get good counts with good shape. Not one or the other but both.


3)    You will not care about the position of the peak we will adjust this in the 20-327.

4)    Acquire a survey and adjust the AES scale factor located in hardware properties until your copper peak is at 920 differentiated. Remember in the scale factor adjustment higher value lowers the peak and lower values raise the peak

5)    Next run an alignment and see where your elastic peak is located. If peak is not at 2K move on to steps 6,7and 8.

6)     Turn the gun off in the software. Turn off the 20-327 drop down the front panel of the 20-327 and extend the bottom board (if you do not have an extender it will take you longer but can be adjusted.

7)    Adjust R47 located toward the back of the board located in diagram 1

8)    Adjust half a turn; replace the board and power up the 20-327 and Augermap software.   Run an alignment determine the direction the pot moves the peak. Adjust accordingly until your alignment is right on 2KV and then run a survey and make sure your Cu1 peak is 920 diff. If peak is not perfect run procedure (step 3 to 8 until elastic peak and Cu1 are in proper positional alignment).

DGC IV calibration

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Years ago RBD Instruments had our DGC IV manufactured by JC Controls.  The DGC IV is basically the same thing as a IG4500.
Although we no longer produce the DGC IV, there are still a few of them in the field.  The calibration procedure is listed below.


PR7(VREF)Reference Voltage Adjust                                                          Direction are with the front

PR4(TC1 Z)TC1 Zero Adjust                                                             of the IG4500 facing you.

PR6(TC2 Z)TC2 Zero Adjust                                                                            N

PR3            TC1 Gain Adjust                                                                                    W –+– E

PR5            TC2 Gain Adjust                                                                                         S

R1(EMIS)    Emission Adjust

PR2(ELEC)Electrometer Adjust


Power Supply Tests ( Ground)

  1. Attach Tester box to controller and check voltages on computer or do steps B,C,D,E
  2. Test -15,+15,+5 from 8 Pin Power Connector Pins   2,3,4.
  3. Turn on Ion Gauge
  4. Test +180 V From Grid Pin (Outside) of tube to Ground.
  5. Test +150 V from Grid Pin to Fil Pin (Outside to Inside) of tube.
  6. Check Degas

(1) Reference Voltage Adjustment

  1. Connect DC DVM from R14{E} to ground R31{E}
  2. Turn on IG4500 while holding down the SELECT switch,.
  3. While holding down the SELECT Switch, adjust PR7 (VREF) until the DC voltage is 10.000 ( +/- .001 )
  4. Release Select Switch and Check off Recorder output box
  5. Turn Power off and on, check that all the LED light up, if so check off Digit(LED) Test

(2) TC1 & TC2 Zero Adjustment

  1. Connect TC Cable to TC1 Input on back of IG4500.
  2. Connect a TC tube that is at Atmosphere to the cable.
  3. Connect DC DVM from R26{E} to ground (R31{E})
  4. Adjust PR4(TC1 Z) until DC Voltage is .133 VDC. (+/- .005 )
  5. Do the same with TC2, Using TC2 Input, R33{E} & PR6(TC2 Z).

(3) TC1 & TC2 Gain Adjustment

  1. Connect TC Cable to TC1 Input on Back of IG4500.
  2. Adjust PR3 through the back panel until the main display is the same vacuum as the Test Tube. Because TC Tubes work by Heat, give the tubes time to readjust after the pot is turned.
  3. Do then same with TC2, Using TC2 Input, Bar Graph & PR5.


(4) Emission Adjustment

  1. Use tester box or connect a current meter in series with Pin 3 of J1 ( Power Connector ).
  2. Connect IG cable to unit and a IG Test Tube. Connect the current source to the BNC on the unit.
  3. Turn on power and turn on ion gauge tube. Use current source to get to 10 mA range
  4. Adjust PR1 (EMIS) until you get 10.0 mA (+/- .05) on current meter.
  5. Use current source to switch down to 1 mA range, emission should be 1.00mA on current meter, Record current.

(5) Electrometer Adjustment

A. Connect current source to IG4500, set to 1uA. Turn on Ion Gauge.

B. Adjust PR2 (ELEC) so IG4500 displays 1.0-04.

C. Repeat Step B for 1nA=1.0-08, 100pA=1.0-09.

D. Also record for 10pA, it should be 1.0-10. (+/- 2.0)


(6) Setpoint & EEPROM

A. Check that the relay turn on and off by listening for them to click

B. Use the computer to set the serial number.

C. Turn unit off and on, Check serial number in “Edit Window” by entering =R#


Technical Modes of IG4500

* Enable Adjust Mode

This mode is for turning the System Enables on and off. It is entered by pressing and holding down the [ION] & [SELECT] buttons while turning on the main power . The display will show The Enable Name followed by either On or Off.

IGS Enables

Enable Name Description
F Filament Enable ( Display Mode )
Fd Full Duplex RS-232 Communication
C1 Code 1 enabled – Filament Overdrive
C2 Code 2 enabled – Under Vacuum, No Collector
C3 Code 3 enabled – Over Vacuum
A Averaging Enabled
E Emission Ranging Enabled


To Adjust the enables press the [ION] switch to select the different enables and the [DEGAS] switch to change from on to off. The Default for the IG4500 is All enables on.

** Timer and Control Mode

This Mode displays the timer value from the electrometer circuit. The value is a 6 digit Hexadecimal number. To put it on the 5 digit display either the lower 5 or the upper 5 digits will be displayed depending on if the high digit is a 0 or not. The Units LED’s are used as status LED’s


Display Unit LED’s

LED Name Status
Torr 25’th Bit of timer
Min Averaging On
mA Full Emission On


Mode 8 is entered by turning the Display switch to Emis. , then press the [ION] & [DEGAS] at the same time. The [ION] button will turn the Averaging on & off, you should make sure Averaging is disabled before adjusting it manually or else the controller will probably switch it back. The [DEGAS] button will switch between Full and 1/10 Emission Current.


20-622 calibration

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Below are the DR11 commands use in the 20-622 calibration procedure. The 20-622 electron gun control is used on the Physical Electronics 660 scanning auger systems.

Command Structure

Use DR11 program or RBD 147 diagnostics  for computer control.

Function                                               Command/Data (hex)

Beam Voltage                                      1ddd

Emission                                             2ddd

Objective Lens                                     3ddd

Iso. Objective Lens                              4ddd

Obj Y                                                  5ddd

Obj X                                                   6ddd

Cond Y                                               7ddd

Cond X                                                8ddd

Reset Overcurrent                                9ddd

Cond Lens                                           Addd


Notes:    – the command and the data are combined in a 16 bit word

– the left-most digit is most significant in address position and data value

– “d” represents a data value in hex

– 000H = 0, 7FFH = 2047 (mid-scale), FFFH = 4095 (max)

Set the CSR (= 1) for proper communication.


 Beam Voltage and Emission

Take the readings from the High Voltage (HV) Programming connector on the back panel. The Beam Voltage reading is taken from pin A and the Emission reading is taken from pin B. The reference is to chassis ground. Note: the bit number in () indicates the only bit set (=1), for troubleshooting purposes.

Command/Data  BV ctrl voltage (V)

1000H                                .001

1100H   (bit 8)                     .625

1200H   (bit 9)                     1.25

1400H   (bit 10)                   2.50

1800H   (bit 11)                   5.00

1C00H                               7.50

1FFFH                              10.00

Check for increasing voltage as you enter the following values in sequence: 1000H, 100FH (bits 0-3), 1010H (bit 4), 1020H (bit 5), 1040H (bit 6), 1080H (bit 7).

Command/Data  Emission ctrl voltage (V)

2000H                                 .001

2100H   (bit 8)                      .625

2200H   (bit 9)                      1.25

2400H   (bit 10)                    2.50

2800H   (bit 11)                    5.00

2C00H                                7.50

2FFFH                               10.00

Check for increasing voltage as you enter the following values in sequence: 2000H, 200FH (bits 0-3), 2010H (bit 4), 2020H (bit 5), 2040H (bit 6), 2080H (bit 7).

Condenser and Objective Lenses

A 200 ohm 2W 10-turn potentiometer must be connected to the Objective Fine Adjustment connector on the back before checking the voltages (Unless it is connected in the electronics bay) . Connect pin D to the pot wiper and connect pins A and C to the pot limits (either order). Set the pot to midway (5 turns for a 10-turn pot).

Note: the bit number in () indicates the only bit set (=1), for troubleshooting purposes. The voltages across the resistors (RX) are taken behind the front panel.

Iso. Objective

 Command/Data  R1-R6 Voltage (V)

4000H                                .016

4100H   (bit 8)                     .304

4200H   (bit 9)                      .610

4400H   (bit 10)                    1.22

4600H                                 1.83

4800H   (bit 11)                     2.44

4A00H                                 3.05

4C00H                                 3.66

4F00H                                 4.58

4FFFH                                 4.88

Check for increasing voltage as you enter the following values in sequence: 4000H, 400FH (bits 0-3), 4010H (bit 4), 4020H (bit 5), 4040H (bit 6), 4080H (bit 7).


Command/Data  R7-R10 Voltage (V)

3000H                                 .021

3100H   (bit 8)                     .322

3200H   (bit 9)                     .645

3400H   (bit 10)                   1.29

3600H                                1.94

3800H   (bit 11)                   2.58

3A00H                               3.23

3C00H                               3.88

3F00H                               4.85

3FFFH                              5.17

Check for increasing voltage as you enter the following values in sequence: 3000H, 300FH (bits 0-3), 3010H (bit 4), 3020H (bit 5), 3040H (bit 6), 3080H (bit 7).


Command/Data  R11-R14 Voltage (V)

A000H                                 .018

A100H (bit 8)                       .469

A200H   (bit 9)                     .939

A400H   (bit 10)                   1.88

A600H                                 2.82

A800H   (bit 11)                     3.76

AA00H                                  4.70

AC00H                                  5.64

AF00H                                  7.05

AFFFH                                  7.50

Check for increasing voltage as you enter the following values in sequence: A000H, A00FH (bits 0-3), A010H (bit 4), A020H (bit 5), A040H (bit 6), A080H (bit 7).


Check for proper centering of the voltages at the Objective and Condenser Steering connector on the back panel.

Command/Data  Between pins, Voltage (V)

57FFH                                   F&H, 0V +/- .4V                  Obj. Y

67FFH                                   E&G, 0V +/- .4V                  Obj. X

77FFH                                   B&D, 0V +/- .4V                  Cond. Y

87FFH                                   A&C, 0V +/- .4V                  Cond. X


20-622 System Test

It is possible for a 20-620 or 20-622 to work on the bench but not focus properly on a system. That is because on the bench the Objective and ISO Objective supplies are tested separately but on the system the objective coil is actually two coils which are tied together. So one of the objective supplies may cave in when connected to the objective coil. You can do a quick test by measuring the voltage across the current resistors behind the front panel of the 20-622 or 20-620.

Voltages for the 20-622 are listed below. The 20-620 should show a similar trend.

20-622   3kV Beam voltage, COND set to 35%, OBJ set to 74.49%, and Objective fine pot set to midrange.

COND .856
OBJ 3.68
ISO OBJ 3.69


20-622   5kV Beam voltage, COND set to 35%, OBJ set to 83.49%, and Objective fine pot set to midrange.

COND 1.076
OBJ 3.85
ISO OBJ 3.47