Campbell Scientific CR10X Measurement and Control System - Manual (Page 89)

SECTION 7. MEASUREMENT PROGRAMMING EXAMPLES
7-5
In the following example, an external temperature
measurement is used as the reference for 5
thermocouple measurements. A Campbell
Scientific 107 Temperature Probe is used to
measure the reference temperature. The
connection scheme is shown in Figure 7.4-1.
If a more accurate reference temperature is
needed, use Campbell Scientific's AM25T Solid
State Thermocouple Multiplexer (Section 8.10).
It uses a 1000 ohm PRT as the reference
temperature and was designed to minimize
temperature gradients across the terminal strip.
The temperature (
°C) of the 107 Probe is stored
in Input Location 1 and the thermocouple
temperatures (
°C) in Locations 2-6.
PROGRAM
01: Temp (107) (P11)
1:
1 Reps
2: 11 SE Channel
3: 1 Excite all reps w/Exchan 1
4: 1 Loc [ Ref_Temp ]
5: 1 Mult
6: 0 Offset
02: Thermocouple Temp (DIFF) (P14)
1:
5 Reps
2: 21
±2.5 mV 60 Hz Rejection
Range
3: 1 DIFF Channel
4: 1 Type T (Copper-Constantan)
5: 1 Ref Temp Loc [ Ref_Temp ]
6: 2 Loc [ TC#1 ]
7: 1 Mult
8: 0 Offset
7.5 107 TEMPERATURE PROBE
Instruction 11 excites Campbell Scientific's 107
Thermistor Probe (or the thermistor portion of the 207
temperature and relative humidity probe) with a 2 VAC
excitation, makes a single ended measurement and
calculates temperature (
°C) with a fifth order
polynomial. In this example, the temperatures are
obtained from three 107 probes. The measurements
are made on single-ended channels 1-3 and the
temperatures are stored in Input Locations 1-3.
CONNECTIONS
The black leads from the probes go to
excitation channel 1, the purple leads go to
analog ground (AG), the clear leads go to
ground (G), and the red leads go to single-
ended channels 1, 2, and 3 (channel 1H,
channel 1L, and channel 2H, respectively).
PROGRAM
01: Temp (107) (P11)
1:
3 Reps
2: 1 SE Channel
3: 1 Excite all reps w/Exchan 1
4: 1 Loc [ 107_T#1 ]
5: 1 Mult
6: 0 Offset
7.6 207 TEMPERATURE AND RH
PROBE
Instruction 12 excites and measures the RH
portion of the Campbell Scientific 207
Temperature and Relative Humidity probe. This
instruction relies on a previously measured
temperature (
°C) to compute RH from the probe
resistance. Instruction 11 is used to obtain the
temperatures of the three probes which are
stored in Input Locations 1-3; the RH values are
stored in Input Locations 4-6. The temperature
measurements are made on single-ended input
channels 1-3, just as in example 7.5. The
program listed below is a continuation of the
program given in example 7.5.
CONNECTIONS
The black leads from the probes are connected
to excitation channel 1, the purple leads are
connected to analog ground (AG), and the clear
leads are connected to Ground (G). The red
leads are from the thermistor circuit and are
connected to single-ended channels 1-3 (1H,
1L, 2H). The white leads are from the RH
circuit and are connected to single-ended
channels 4-6 (2L, 3H, and 3L). The correct
order must be maintained when connecting the
red and white leads; i.e., the red lead from the
first probe is connected to single-ended channel
1H and the white lead from that probe is
connected to single-ended channel 2L, etc.
PROGRAM
(continuation of previous example)
02: R.H. (207) (P12)
1:
3 Reps
2: 4 SE Channel
3: 1 Excite all reps w/Exchan 1
4: 1 Temperature Loc [ 107_T#1 ]
5: 4 Loc [ RH#1 ]
6: 1 Mult
7: 0 Offset