OM-550
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35
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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.
