Lake Shore Model 331 Temperature Controller User’s Manual
8.9.5.1
Analog Output Calibration
Purpose
To determine the analog output offset and gain errors and provide offset and gain calibration
constants back to the Model 331.
Process
1. Reset the calibration constants to their default values using the
CALRSTZ
and
CALRSTG
commands.
EXAMPLE:
Zero Offset Reset Command:
CALRSTZ V,1
Gain Reset Command:
CALRSTG V,1
2. Connect the 100 k
Ω
resistor to the analog output. Connect the positive lead of the DMM to the
analog output positive terminal, the negative lead is connected to the analog output negative
terminal.
3. Set the analog output to manual mode, bipolar mode on, manual output of –100 %. Read the
output voltage with the DMM to a tolerance of ±0.0010 VDC and record this negative full scale
(–FS) value.
4. Determine the offset calibration constant by dividing the –FS value by 10, adding 1, and then
negating the result.
5. Use
the
CALZ
command to send the offset calibration constant.
EXAMPLE:
–FS DMM Reading: –10.0564
Offset Constant Calculation: -((-10.0564/10) + 1) = 0.00564
Calibration Command:
CALZ V,1,0.00564
NOTE:
Be careful to use the formula described above and not use the same process that
calibrates the zero offset of the inputs.
6. Set the analog output to +100 %. Read the output voltage with the DMM to a tolerance of
±0.0010 VDC and record this positive full scale (+FS) value.
7. Determine the gain calibration constant by negating the –FS reading obtained in Step 3 and
adding the +FS reading to the result and then dividing that number into 20.
8. Use
the
CALG
command to send the gain calibration constant.
EXAMPLE:
+FS DMM Reading: 10.0432
–FS DMM Reading: –10.0564
Gain Constant Calculation: 20/(10.0432+10.0564) = 0.99504
Calibration Command:
CALG V,1,0.99504
9. Send
the
CALSAVE
command to save the constants in the E
2
prom.
8-16
Service
