PicoLog Self-Help Guide
AR346-1
© Copyright 2014 Pico Technology Ltd.
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Note:- Lookup tables seem to have a limit of 14 lines. Above that, use a Scaling File.
See below:-
If you use a scaling file you must ensure that either:-
1. All parameter formatting is done on the parameter formatting page only and none in
the scaling file (just the equation or look-up table).
or:
2. Parameter formatting is NOT ticked and all formatting is done in the scaling file only.
Duplication of parameter formatting will cause a crash!
To use a Scaling file instead of Equation or Table Lookup
If you are using, for example, a thermistor, type:-NJ28 RA 0104 FCC (100k ohm @
25 °C) and you are using a 47 kilohm resistor as a load resistor to the +2.5V reference
to give a working range of 5 °C to 145 °C.
The PicoLog 1012 has an input resistance of 1 MΩ and this is in parallel with the
thermistor. Thus the thermistor resistance value is reduced to:
(100 x 1,000) / (100 + 1,000) kΩ = 90.91 kΩ (@25 °C)
The +2.5 V sensor supply of the PicoLog 1012 is fed through the 47 kΩ resistor to the
thermistor wired across the input channel and @25 °C the voltage at their junction will
be:
(2.5 x 90.91) / (90.91 + 47) volts = 1.648 V.
Doing the same calculations from 0 °C to 150 °C gives values:-
2.023(V) = 5 (deg C)
1.853 = 15
1.648 = 25
1.419 = 35
1.185 = 45
0.964 = 55
0.767 = 65
0.602 = 75
0.468 = 85
0.363 = 95
0.282 = 105
0.219 = 115
0.171 = 125
0.135 = 135
0.107 = 145