Campbell Scientific TC Psychrometer PROM and Cooling Current Interface (S3497X, A3497) - Manual (Page 8)

25 PELTIER THERMOCOUPLE PSYCHROMETER
4
6. OUTPUT FORMAT
Instruction 25 stores all readings from a given
TCP sequentially in Input Storage. The base
temperature is first, followed by the zero
reading, and then the sequence of wet-bulb
readings with the zero reading subtracted. The
series of readings from the next TCP then
follows, etc. The number of Input Storage
locations allocated must be based upon the
number of TCPs excited by one A3497
Interface and the number of wet-bulb readings
per TCP. When the Loop Instruction is used,
the readings from each A3497's TCPs use the
same Input Storage. The readings associated
with a given A3497 must be transferred to Final
Storage before progressing to the next A3497.
All the readings associated with one A3497 can
be transferred to Final Storage using a single
Sample Instruction (#70) and the appropriate
number of "repetitions." However, this
technique results in the reading from all the
TCPs being blocked together in one Output
Array. By setting the Output Flag and using a
Sample Instruction for each TCP associated
with the A3497, the readings for each TCP are
blocked into their own Output Array and contain
their own unique Output Array ID. An example
of this latter type of output is shown in Table 2.
7. EXAMPLE
The following program example was used to
generate the data shown in Table 2. Four
Model PST-55 Wescor and four Model 74
Merrill TCPs were read using two A3497
Interfaces. The program makes use of the
Loop Instruction. The following criteria were
used:
1. Number of wet-bulb readings per TCP - 29
2. Heating/cooling current - 4.5 mA (-1900 mV)
3. Heating duration - 5 s
4. Delay after heating - 15 s
5. Cooling duration - 15 s
6. Delay after cooling - 0 s
7. Delay between wet-bulb measurements - 0 s
8. Input Storage (31 locations per TCP):
First TCP Loc 2 - Loc 32
Second TCP Loc 33 - Loc 63
Third TCP Loc 64 - Loc 94
Fourth TCP Loc 95 - Loc 125
9. Input Card - 1
10. First measurement channel - 1
11. Excitation Card - 1
12. First excitation channel - 1
Acknowledgment: CSI gratefully
acknowledges the assistance of Dr. Raymond
W. Brown, U.S. Forest Service, Intermountain
Forest and Range Experiment Station, Logan,
Utah and the use of his facilities in testing the
TCP software.
01: P 17 Panel Temperature
01: 1 IN Card
02: 1 Loc [:Panel T ]
02: P 87 Beginning of Loop
01: 0 Delay
02: 2 Loop Count
03: P 25 Thermocouple Psychrometer
01: 4 Psychrometers per A3497
02: 2 Loc:[:TCP 1 #1 ]
03: 1 Ref Temp Loc Panel T
04: 2 2=Measure HI WRT GND,
1=LO
05: 1 IN Card
06: 1 IN Chan
07: 1 EX Card
08: 1 EX Chan
09: -1900 mv Excitation
10: 1500 Heating (time units=.01sec)
11: 1500 Delay before 0 measurement
12: 1500 Cooling duration
13: 0 Delay before wet bulb meas.
14: 0 Delay between wet bulb meas.
15: 29 Wet bulb measm'ts per psychr.
04: P 86 Do
01: 10 Set high Flag 0 (output)
05: P 70 Sample
01: 31 Reps
02: 2 Loc TCP 1 #1
06: P 86 Do
01: 10 Set high Flag 0 (output)
07: P 70 Sample
01: 31 Reps
02: 33 Loc TCP 2 #1
08: P 86 Do
01: 10 Set high Flag 0 (output)
09: P 70 Sample
01: 31 Reps
02: 64 Loc TCP 3 #1
10: P 86 Do
01: 10 Set high Flag 0 (output)