Campbell Scientific CR510 Basic Datalogger User Manual
Page 95
SECTION 7. MEASUREMENT PROGRAMMING EXAMPLES
7-17
04:
Z=X+F (P34)
1:
1
X Loc [ Temp ]
2: -24
F
3:
3
Z Loc [ Temp_Comp ]
05:
Z=X*F (P37)
1:
3
X Loc [ Temp_Comp ]
2:
-.0698
F
3:
3
Z Loc [ Temp_Comp ]
06:
Z=X+Y (P33)
1:
3
X Loc [ Temp_Comp ]
2:
2
Y Loc [ Pressure ]
3:
2
Z Loc [ Pressure ]
07:
IF (X<=>F) (P89)
1:
5
X Loc [ Cmpile_Ck ]
2:
1
=
3:
0
F
4:
30
Then Do
08:
Z=X+F (P34)
1:
2
X Loc [ Pressure ]
2:
47.23
F
3:
4
Z Loc [ Offset ]
09:
Z=F (P30)
1:
1
F
2:
0
Exponent of 10
3:
5
Z Loc [ Cmpile_Ck ]
10:
End (P95)
11:
Z=X-Y (P35)
1:
4
X Loc [ Offset ]
2:
2
Y Loc [ Pressure ]
3:
6
Z Loc [ Distance ]
7.14 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 CR510 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 1. The CURS100 TIM and dew
point sensor are wired to the CR510 terminal
strip panel as shown in Figure 7.14-1.
PROGRAM
01:
Volt (Diff) (P2)
1:
1
Reps
2: 25
±
2500 mV 60 Hz Rejection
Range
3:
1
DIFF Channel
4:
1
Loc [ Dew_Pnt_C ]
5:
.06875 Mult
6: -67.5
Offset
INPUT LOCATIONS
1 Dew_Pnt_C