Measurement Computing DataShuttle - Manual (Page 122)

Appendix A-2 1 1-13-01 DataShuttle and DynaRes
• You can calibrate to your own temperature measurement by adjusting CCAL in the Calib.Dat file. Add
75 points to the number for every needed 1°C increase in the reading. Starting at 22,000 for CCAL is a
good idea.
• If you see very negative temperatures (like -700 F) then you probably have an open thermocouple. The
ends of the thermocouple must be re-attached, though care must be taken when doing this. If intermit-
tent low temps are encountered then the source is probably noise. On a type K thermocouple 4µV can
cause 0.1°C change. This means that 360mV will show up as ±9,000°C.
• For long thermocouple or extension wire, a shield should be used. This will reduce noise. A shield
consists of a conductive conduit, through which the thermocouple wire is passed. This conduit is in
turn connected to ground (GND not GND(A)). In this way any noise is transmitted through the shield
to ground instead of through the thermocouple wire.
• Thermocouple wire should not be excessively long. Instead of using long wires, attach extension wire
matched to the type of thermocouple. If the extension wire is twisted pair, then noise reduction will be
increased.