Cr1000 Program Example - Campbell CURS100 Instruction Manual

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 ─ y 1 ) = m (x ─ x 1 )
Solve the equation for m that is the slope of the line (or multiplier).
m
Now replace the known values to determine the intercept (or offset). Where y
= m(x) + b
200
=
b
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
CURS100 100 Ohm Current Shunt Terminal Input Module
−
700 psi 200 psi
= =
0 3125 .
−
2000 mV 400 mV
psi
= × +
psi . 0 3125 400 mV
mV
− × =
200 . 0 3125 400 75 psi
psi
mV
b
9