WIKA operating instructions, model CTH7000
EN
27
08/2020 EN/BG
4. Design and function
■
CVD coefficients - Callendar van Dusen used for calibrated industrial or low alpha
PRT’s of 0.00385.
■
ITS-90 coefficients - used for calibrated high alpha PRT’s of values 0.003926 to
0.003928.
The choice of conversion method and the relevant coefficients are set from this menu.
For thermistors, the instrument provides one standard algorithm for converting resistance
to temperature.
■
Steinhart and Hart
c. Probe coefficients
Both PRT and thermistor probes must be correctly calibrated to produce their most
accurate performance. The CTH7000 can store calibration data for each of the two
channels; this information is only required when passive probes are being used. When
smart probes are used, the calibration data is stored in the probe and the coefficients
held in the CTH7000 are not required or used.
Smart probes use their own internal calibration data. The instrument
coefficients are ignored when a smart probe is attached.
When passive probes are used, correct entry of the parameter values is absolutely
critical to obtain accurate readings. For this reason, the coefficients menu is pass code
protected. The pass code screen (below) will appear once the
Coefficients
menu has
been selected.
Use
the
[Up]
and
[Down]
arrow keys to increment or decrement the pass
code value.
