Lake Shore Model 234/234D User’s Manual
3-2
Operation
PCB DIP Switch Settings (Continued)
Current/Voltage (I/V) OUT is for selection of proper output type. Open is for
4–20 mA and closed is for 0–20 mA. The 4–20 mA is an industry standard,
while the 0–20 mA translates output into voltage scaled up to 10 V. For a
0-10 V output, use a 500
Ω
±0.02% output load resistor across the OUT+
and OUT– terminals. Load resistors less than 500
Ω
can convert the output
to voltage using the following formula:
.
Unless otherwise specified, units ship from the factory with the DIP switch
set with I/V OUT open (4-20 mA).
3.2
OUTPUT TO TEMPERATURE CONVERSION
Output current or voltage are directly proportional to the temperature
reading. For the 4-20 mA output, the following formula converts output
current to temperature:
where
T
= temperature in kelvin,
I
OUT
= output current in mA, and
A
and
B
are constants (from Table 3-1) depending on temperature.
For the 0-20 mA output (using a 500
Ω
resistor for 0-10 V), this formula
converts output voltage to temperature:
where
T
= temperature in kelvin,
V
OUT
= output voltage, and
C
and
D
are
constants (from Table 3-1) depending on temperature.
Table 3-1. Conversion Parameters for Temperature in K
4–20 mA
0–10 V
RANGE
TEMP. (K)
A (K)
B (K/mA)
C (K)
D (K/V)
RANGE1
0 – 10
–2.5
0.625
0
1.0
RANGE2
0 – 20
–5.0
1.25
0
2.0
RANGE3
0 – 100 –25.0
6.25
0
10.0
RANGE4
0 – 200 –50.0
12.5
0
20.0
RANGE5
0 – 300 –75.0
18.75
0
30.0
RANGE6 75 – 325
12.5
15.625
+75
25.0
Summary of Contents for 234
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