# Adjusting a Transmille Unit Remotely (3000A, 4000, 9000A) - DC Voltagege and DC Current

Modified on Tue, 24 Oct, 2023 at 4:16 PM

Step 1 : Set the range that you wish to adjust

Step 2 : Enter calibration mode by sending the command a1

Step 3 : Read back the calibration factors for the range

"CALIBRATION:PRINT" will respond with the calibration factors for the range, separated by carriage return line feeds in the following order

POSITIVE FACTOR<CR><LF>
NEGATIVE FACTOR<CR><LF>
ZERO FACTOR<CR><LF>
MISC FACTOR<CR><LF>
*0<CR><LF>

The *0 indicates the end of the response

An example can be found below :

279486223
27947905
3832
268435456
*0

DC Ranges use the Positive Factor, Negativefactor, and the Zero factor
AC Ranges use the Positive Factor and Zero Factor, as well asan additional array of flatness corrections

Resistance Ranges use the Positive factor for 2 Wire values, Negative factor for 4 wire values, and in the case of 1000A, 3000A and 9000A, the Zero factor for the simulated zero, and the misc factor for the Full scale simulated factor

Step 4 : - Adjusting the ZERO factor

Calculate the difference between the measured output and the nominal setting, and then convert to base units (i.e. Volts or Amps)

I.e.

0.001mV - 0.000mV = 0.001mV = 0.000,001V

Depending on the series of unit, there is a different Zero multiplier required

1000A/1000B

Voltage

100mV  ZBit = 0.000,000,001

1V         ZBit = 0.000,000,01

10V       ZBit = 0.000,000,1

100V     ZBit = 0.000,001

1000V   ZBit = 0.000,01

Current

100uA:      ZBit = 0.000,000,000,001

1mA:        ZBit = 0.000,000,000,01

10mA       ZBit = 0.000,000,000,1

100mA     ZBit = 0.000,000,001

1A            ZBit = 0.000,000,01

10A          ZBit = 0.000,000,1

3000A / 4000 / 9000A

Voltage

200mV :      ZBit = 0.000,000,001

2V:              ZBit = 0.000,000,01

20V:            ZBit = 0.000,000,1

200V:          ZBit = 0.000,001

1000V:        ZBit = 0.000,01

Current

200uA :       ZBit = 0.000,000,000,001

2mA:           ZBit = 0.000,000,000,01

20mA:         ZBit = 0.000,000,000,1

200mA:       ZBit = 0.000,000,001

2A:              ZBit = 0.000,000,02

22A / 30A : ZBit = 0.000,000,2

The new Zero factor is then calculated as below

Old Zero Factor - ((Difference / Zbit) * -1)

Worked example

3832 - ((0.000,001 / 0.000,000,001) * -1) = 4832

After performing the calculation, send the new calibration factor back to the unit with the following command :

"Z" followed by the new factor.

Figure out the percentage error.

i.e.

((1.005 - 1.000) / 1.005) * 100 = 0.49751

Positive Factor - (Positive Factor * Percentage Error) / 100

Do the same for the NEGATIVE factor if required.

Valid factors are TYPICALLY between 241591911 and 295279001; if the calculation is outside of these parameters, there is an error in the measurement or readback.

Note - the calibration factor is always positive

Step 7 : Storing Calibration

Send the new factor back to the calibrator.

If a POSITIVE factor, send the command "P" + the new factor
If a NEGATIVE factor, send the command "N" + the new factor

Step 8 : Re-run the test

Step 9 : Save calibration factors

Note - you MUST save calibration factors before changing range or turning the unit off. Changing range before saving the calibration factor will result in the adjustment being lost

Send the command "a2" to store the new calibration