NetScan User’s Manual Calibration 6-19
4. Type U2X to verify calibration mode. U128 should appear, indicating the unit is in calibration mode.
5. Enter commands similar to those in the first two columns in the following table. This example is for a
T/C card in slot #1, and a Type 3 (“T” type) thermocouple. The table on the preceding page provides
additional channel numbers to use as they apply to your system.
Enter: J3,3,0000.0X After each calibration enter U2X,
J6,3,0000.0X then observe U128 indicating no errors.
J11,3,0000.0X
J14,3,0000.0X
Note: The number after the J is the channel number, the next number is the thermocoupl e “type, ” and the
number preceding the X is the temperature in °C. Thus, J3,3,0000.0X means “Calibrate cold
junction offset for channel 3, type 3 (T-type) thermocouple at 0°C.
Response codes and meanings applicable to calibration are as follows:
Response to U2X Indication for Calibration Mode
U128 No error
U129 Read Failure (EEPROM Error)
U130 Write Failure (EEPROM Error)
U132 Chksum Err (EEPROM Error)
U136 Cal Err (offset, gain, or temperature sensor out of range)
U144 Invalid password
U160 Invalid command
7. Verify calibrated temperature using one of the following three options. Note related figure on
following page.
a) Cold Cell Method. Connect Cold Cell simulator to the T/C card’s 4 CJC reference channels and to the
DC voltage calibrator, as indicated in the following illustration, figure (a). Adjust the calibrator
voltage to match that of the desired test temperature using Voltage-to-Temperature Reference Tables.
Verify the channel readings match the test temperature for each of the four CJC reference channels.
Repeat verification for all T/C cards.
Note: The Cold Cell Simulator in figure (a) shows a special connection box attached to it. This
connection box, which can be easily made, is not part of the cold cell device.
b) Hot Cell Method. Connect Hot Cell simulator to T/C card’s first CJC reference channel. Adjust Hot
Cell to obtain desired test temperature and ensure temperature is stabilized. Observe channel reading
to match test temperature. Repeat test for remaining three CJC reference channels. Repeat verification
for all T/C cards.
c) T/C Calibrator Method (see note). Connect a thermocouple calibrator/simulator to the first
ChartScan, or NetScan, CJC channel in accordance with the calibrator/simulator manufacturer’s
instructions. Certain simulators will require the use of specific type T/C extension wire to create a
cold junction at ChartScan’s, or NetScan’s, input; while other simulators require copper wire and
reduce the output voltage as a function of ambient temperature to create the effect of a cold junction at
the main unit. Adjust the output setting to the desired temperature and verify the channel reading is
within the range of ChartScan’s, or NetScan’s, tolerance band for the T/C type and temperature.
Repeat test for remaining three CJC reference channels. Repeat this test for all thermocouple type
signal conditioning cards.
The T/C Calibrator/Simulator Method is not recommended because, unlike voltage
calibrators, T/C Calibrator/Simulators have no provisions for remote sensing (and are
therefore more readily subject to the transient effects of sampled data acquisition
systems, such as ChartScan and NetScan). These transient effects can cause erroneous
readings, even when both units are calibrated within specifications.