Physitemp Instruments TH8 - Manual (Page 6)

mometer calibration data, and convert from Centigrade to Fahrenheit if necessary by mutiplying
by 9/5 and adding 32. Compare this reading with that of the Model TH-8. Note both Fahrenheit
readings and any differences on a record sheet.
(c) Move the slide switch to the degrees C position. Stir the water bath another time, and
again compare the standard thermometer reading with that of the instrument. Record both
Centigrade readings and any difference.
6.5 CHECKING THE HIGH END OF THE TEMPERATURE RANGE
(a) Fill the other thermos flask with a mixture of hot and cold water to produce a temperature
of approximately 45°C (113°Fahrenheit).
(b) Using the second standard mercury-in-glass thermometer with the second thermocouple
sensor attached, stir the bath well and wait 10 minutes.
(c) Repeat step 6.4 (b) for checking high end of the range. Recheck the low end of the tem-
perature range to ensure that no change has occurred. If change has occurred, repeat the entire
calibration procedure.
6.7 Allowing for some reading error in mercury themometer (there can be none with the digi -
tal instrument display) and possible probe error, readings should agree within the limits noted in
section 9.7. This means, as an approximate rule of thumb, that the difference between standard
and instrument readings should not exceed 0.2°C or 0.4°F. The exact error limits depend on the
actual temperature at which the calibration is checked.
6.8 If the instrument appears to be out of calibration based on the foregoing checks, it should
be returned for service (see section 12).
Please note - these calibration instructions will provide a calibration accuracy of not
better than ±0.2°C. A more accurate method requires the use of a temperature controlled oven
and potentiometric facilities in place of the water baths described above. Please consult the
Service Dept. at Physitemp for details.
7.0 THERMALERT AUXILIARY OUTPUT
If your TH-8 has been supplied with the analog out-
put option, the pins are connected as follows:
Pin 2 - analog output positive
Pin 6 - analog output return
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