Omega Vehicle Security freedom OM-550 - Manual (Page 40)

OM-550 u 35 u
4.14.5 MATCHING AND SCALING A VOLTAGE TRANSDUCER
EXAMPLE: Given a 20 - 90 % RH (Relative Humidity) transducer with a 0 - 10 VDC
output at a maximum current of 3 mA.
Program the OM-550 to indicate 20.00 %RH to 90.00 %RH (that is, to indicate %RH
with 0.01% resolution).
If a ±10 Voltage Probe is being used, begin with step 3, below. (This probe is already
matched to the OM-550).
1. First, find the Matching resistors:
I = 1/2 maximum current
= 0.003 / 2
= 0.0015 Amps
R1 = 2 / I R2 = (V - 2) / I
= 2 / 0.0015 = (10 - 2) / 0.0015
= 1333
Ω
= 5333
Ω
2. Check:
V= (R1 + R2) * I V = R2 * I
= (1333+5333)*1.5 mA = 1333*1.5 mA
= 9.999 = 1.9995
= 10 = 2
With these matching resistors the OM-550 will see a max 2 VDC at the Transducer max
output of 10 VDC.