21
5.5 Thermal Calibration
Be sure to allow the Heat-Prober to stabilize to room temperature for at least 1/2 hour
before calibration. It is important that all components be allowed to stabilize to room
temperature especially those components involved with cold junction compensation.
Place a probe connected to the Heat Prober into a 0°C (ice/water bath mixture). Adjust
R9 until 0°C (32°F) is read. Then put the probe in a higher known bath temperature,
and adjust span at R22 until this reading is achieved.
NOTE:
Thermocouple wire has an allowable manufacturing tolerance. Even though the
instrument is characterized with much higher accuracy, any particular thermocouple
measuring system may have an error contributed by the thermocouple. Standard Type
K thermocouples, for example, have a manufacturing tolerance of ±2°C from 0° to
1370°C. Therefore, the above “thermal calibration” may actually introduce an error
into the meter because it is being calibrated to a thermocouple with an error in it.
Wahl thermocouple probes are precalibrated at 2 temperatures with an acceptable
tolerance of ±O.1°F/C.
Wahl
Calibrator P/N
Thermocouple
Type
Heat-Prober
Model No.
TA-70A
K (Yellow)
2500M
2500MX
1370M
1370MX
TA-70S
S (Green)
3200MF
3200MFX
1770MC
1770MCX
Figure 5-1. Wahl Calibrator Types
Summary of Contents for 2500MX
Page 8: ...4 Figure 2 1 Digital Heat Prober Major Features...
Page 14: ...10 Figure 3 2 Standard Wahl Probes Figure 3 3 Extension Probe Handle...
Page 16: ...12 Figure 3 4 Molten Metal Dipstick...
Page 28: ...24 Figure 5 2 Heat Prober with Wahl Calibrator...
Page 29: ...25 TP2 R29 R9 R20 TP1 R22 TP3 U 3 Figure 5 3 LED Adjustment Points...
Page 30: ...26 TP2 R29 R9 R20 TP1 R22 TP3 U 3 Figure 5 4 LCD Adjustment Points...
Page 32: ...28 Figure 6 1 Program Flow Chart...
Page 43: ...39 Figure 8 1 Block Diagram...
Page 44: ...40 Figure 8 2 LED Component Layout...
Page 45: ...41 Figure 8 3 LCD Component Layout...
Page 54: ...50 Figure 11 1 2500M Accessories and Special Purpose Probes...
