User's Manual

CALIBRATION
TEC Calibration Procedures
18 TCM-39032
CHAPTER 3
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Remote Operation ITE Current Calibration
The following procedure is for calibrating the ITE constant current source for both
polarities of current. This procedure calibrates the zero current set point
automatically, then it automatically drives the TE current output to internally set
limits of +
1 amp. When each of these values is reached and is stable, the user
enters the actual value of the current, as measured by an external DMM. The
LDC-3900 then automatically calibrates the TEC current source and limits.
This procedure is for remote (GPIB) operation.
1 With the output off, connect a 1 Ω, 10 W resistor across the TEC output terminals and use
a calibrated DMM to measure the voltage across the resistor. Calculate the current in the
following steps by using Ohm’s Law:
I = E / R
- where E is the accurately measured voltage across the resistor, and R is the accurately
measured load resistance. (A 4-point probe resistance measurement is recommended.)
2 Enter the “TEC:CHAN x” command over the GPIB to select the channel of the TCM-
39032 to be calibrated, where x = the channel number. Enter the “TEC:OUTPUT OFF”
command to force the output off.
Enter the “TEC:CAL:ITE” command over the GPIB to place the TCM-39032 in is TEC
Current Calibration mode. The LDC-3900 will automatically calibrate its zero output
current and beep when it is ready to continue. If the TEC output is not off, the TEC current
calibration mode cannot be entered.
The TCM-39032 will first perform a zero point calibration. This takes about 20 seconds.
Then it will set the output to 1 Amp, for calibration.
3 When the LDC-3900 is ready for the actual TEC current value to be entered, a remote
query of “TEC:CAL:ITE?” will return a response of “1”.
When the measured value (actual ITE) is stable and the LDC-3900 is ready to proceed,
enter the value by issuing the “TEC:ITE <nrf value>” command, where the absolute value
of the actual ITE measurement is the <nrf value>.
To ensure measurement stability of the actual I value when the measurement is taken as
a part of an automated test, the DMM measurement should be polled in a loop. When the
measured value is consistent within one digit for 5 seconds (for example), the actual I
value could be considered stable.
4 Once the actual ITE value is entered via the “TEC:ITE” command, the new calibration
value is stored into non-volatile memorey on the TCM-39032. The LDC-3900 will then be
ready for the User to enter the limit calibration value for its negative polarity output.
5 Repeat steps 3 and 4 for the negative polarity of the TEC output current (entering the
absolute value of the measurement). After the value for the negative polarity of the TEC
output is entered, the TCM-39032 will automatically calibrate its current limits and set
points. After a few seconds, the LDC-3900 will return to it’s former state (before
calibration). The LDC-3900 will beep when it has finished storing all of the new calibration
values.