Campbell Scientific CURS100 100 Ohm Current Shunt Terminal Input Module - Manual (Page 15)

CURS100 100 Ohm Current Shunt Terminal Input Module
and at 700 psi is:
V = 0.020 × 100
V = 2.0 V or 2000 mV
Since the datalogger measures in mV, the multiplier (or slope) must be in units
of psi/mV. Therefore, the y values have the units psi and the x values mV.
The equation of a line is:
(y ─ y1) = m (x ─ x1)
Solve the equation for m that is the slope of the line (or multiplier).
m
psi psi
mV mV
psi
mV
=
−
−
=
700 200
2000 400
0 3125 .
Now replace the known values to determine the intercept (or offset). Where y
= m(x) + b
psi b
b mV
mV
psi
psi
75 400 3125 . 0 200
400 3125 . 0 200
= Ч − =
+ Ч =
m = multiplier (slope) = 0.3125 and
b = the offset (intercept) = 75.0.
5.3 CR1000 Program Example
'CR1000 program example for sensor with 4-20mA output.
'Assuming a flow meter that outputs a 4-20mA signal representing 0 - 100 gal/min,
'the voltage across the resistor at 0 gal/min = 4mA * 100 ohms = 400mV,
'and at 100 gal/min is 20mA * 100 ohms = 2000mV. The change in mV is
'2000mV - 400mV = 1600mV for 0 - 100 gal/min flow rate.
'The measurement result (X) for the VoltDiff instruction is mV. The
'multiplier to convert mV to gal/min is: mV * 100gal/min / 1600mV = 0.0625,
'the offset is 400mV * .0625 = -25.0.
Public Measure
DataTable (Hourly,True,-1)
DataInterval
(0,60,Min,0)
Average (1,Measure,IEEE4,0)
EndTable
9