Campbell CR23X, Operator'S Manual

Page: 108 / 374

SECTION 7. MEASUREMENT PROGRAMMING EXAMPLES
7-20
;Find Temperature and Pressure.
;
04: Paroscientific (P64)
1:
1 Loc [ Temp_us ]
2: 19 Loc [ Temp_C ]
* Table 3 Subroutines
01: Beginning of Subroutine (P85)
1:
1 Subroutine 1
02: Bulk Load (P65)
1:
5.8603 F
2: -3970.3 F
3: -7114.3 F
4: 102.78 F
5: 70.294 F
6: 6.6101 F
7: -119.29 F
8: 30.884 F
9: 3 Loc [ U0 ]
03: Bulk Load (P65)
1:
0 F
2: 26.337 F
3: .85170 F
4: 21.801 F
5: 0 F
6: 0 F
7: 1 F
8: 0 F
9: 11 Loc [ D2 ]
04: End (P95)
End Program
INPUT LOCATION LABELS:
1 Temp_us 12 T1
2 Press_us 13 T2
3 U0 14 T3
4 Y1 15 T4
5 Y2 16 T5
6 Y3 17 Comp_Chk
7 C1 18 plce_hold
8 C2 19 Temp_C
9 C3 20 Press_psi
10 D1 21 Signature
11 D2
7.17 4 TO 20 MA SENSOR USING
CURS100 TERMINAL INPUT
MODULE
A dew point sensor has a 4 to 20 mA output
over the dew point temperature range of -40
°
to
+70
°
C. The dew point sensor output may be
measured by the CR23X using the CUS100
Terminal Input Module (TIM). The CUS100
uses a 100
Ω
,
±
0.01 % resistor to convert the 4
to 20 mA range to 400 to 2000 mV. The
millivolt range was found using the relationship
V = IR, where V is voltage, I is current, and R is
resistance, e.g. the voltage at -40°C is given by
V = 4 mA
∗
100
Ω
= 400 mV. The dew point
sensor is measured with Instruction 2 (Volt Diff).
The multiplier for dew point temperature is
found with the following relationship [70°C -
(-40°C)] / [2000 mV - 400 mV] = 0.06875°C/mV.
The offset is found by taking the linear
relationship °C = mV
∗
Mult + Offset and solving
for the Offset. At -40°C the voltage is 400 mV,
thus the Offset = -40 - [400 mV
∗
0.06875°C/mV] = -67.5°C.
CONNECTIONS
The dew point sensor is measured with a
differential voltage measurement on differential
analog input 4. The CURS100 TIM and dew
point sensor are wired to the CR23X wiring
panel as shown in Figure 7.17-1.
PROGRAM
01: Volt (Diff) (P2)
1:
1 Reps
2: 25
±
5000 mV Slow 60 Hz
Rejection Range
3: 4 DIFF Channel
4: 1 Loc [ Dew_Pnt_C ]
5: .06875 Mult
6: -67.5 Offset
INPUT LOCATIONS
1 Dew_Pnt_C