Heat-Prober
®
Platinum-RTD Thermometers User Manual
21
6.8 Fahrenheit to Centigrade Conversion
The Heat-Prober can be ordered as a °F or °C unit. The 392 will read out in
°F unless a jumper is in place
between terminals “A” and “B” on the PC Board. When jumped an
equivalent reading of what was displayed in °F will be displayed in °C. The computer makes the
calculation and there is no adjustment. “D” versions will have a front panel switch for selecting
between °F and °C.
6.9 Open Probe Display
Remove the calibrator or decade box from the meter while the power is on.
The display should show -OL-.
If power is turned on while probe is absent, the same display should occur.
6.9.1 “Help” Display
(Appears on 392E or 392M only, 392EX or 392MX does not display
“Help”)
The microcomputer is programmed to display “Help” when span adjustment outside the normal
range is attempted. If “Help” continues to be displayed, it indicates that an incorrect adjustment
is being attempted or a faulty meter.
7.0 THERMAL CALIBRATION PROCEDURE
For thermal calibration of temperature, baths are needed for immersion probes, and surface
plates are used for surface probes. However, remember that calibrating with a specific probe will
introduce the error of the probe into the meter system. Other probes may therefore introduce
greater or lesser error, because the meter is moved away from its nominal curve. DO NOT
calibrate a surface probe by immersion. There will be an error because compensation is made
at the factory for heat loss in surface probes.
Insert the probe in the unit and into well stirred, controlled ice baths at 0°C. (Be sure it is well
stirred). The temperature can vary 1°C, depending on the layer of water the probe is in, or
proximity to a piece of ice.
With the top cover removed (as explained in
Section 6.2
) and instrument open, adjust until the
0.0 reading is obtained.
For span, a 250°C or higher bath, should be used. Adjust R35 until the temperature reading is
achieved.
