Campbell Scientific CR10X Measurement and Control System - Manual (Page 105)

SECTION 7. MEASUREMENT PROGRAMMING EXAMPLES
7-21
TIME OUT, PARAMETER 5
The "time out", Parameter 5, specifies the
maximum length of time the instruction waits on
each repetition to receive the number of cycles
specified in Parameter 4. The time out units are
0.01 seconds. The minimum time out is the
time required to receive the specified number of
cycles at the maximum expected frequency.
Time out calculations using a recommended
9000 and 5000 cycles for temperature and
pressure at the maximum frequency are shown
below.
Time out for temperature: 6,
5.22 = (5.8
∗10 -6 )(9000/0.01)
Time out for pressure: 16,
15.5 = (3.1
∗10 -5 )(5000/0.01)
If the time out expires before the requested
number of cycles are read, -99999 is stored in
the input location (Parameter 6). After reading
the correct number of cycles, program
execution advances to the next instruction; the
time out may be over estimated without losing
execution speed.
CONVERTING MICROSECONDS TO °C AND PSI
Instruction 64 (Paroscientific Processing)
reports the temperature in
°C and the pressure
in PSI using the measurements made by
Instruction 27 (period average).
The pressure (P) and temperature (T) in
microseconds are converted to psi and
°C
according to the following relationships provided
by Paroscientific.
P = C (1-T
0
2
/Tau
2
)(1-D(1-T
0
2
/Tau
2
))
T = Y
1
U + Y
2
U
2
+ Y
3
U
3
where:
C = C
1
+ C
2
U + C
3
U
2
D = D
1
+ D
2
U
T
0
= T
1
+ T
2
U + T
3
U
2
+ T
4
U
3
+ T
5
U
4
U = U
t
- U
0
Tau= measured period, in microseconds, of
pressure
U
t
= measured period, in microseconds, of
temperature
Values for the calibration coefficients (U
0
, Y
1
,
Y
2
, Y
3
, C
1
, C
2
, C
3
, D
1
, D
2
, T
1
, T
2
, T
3
, T
4
, T
5
)
are provided by Paroscientific.
ENTERING THE COEFFICIENTS
Coefficients are entered using CR10X
Instruction 65 (Bulk Load). A calibration sheet
from Paroscientific which accompanies the
transducer lists the 14 coefficients. Table 7.17-
3 shows the correct format for entering the
coefficients. The coefficients shown are for
transducer Serial Number 30135. Your
coefficients will be different.
TABLE 7.17-3 Coefficient Entry Format for
Paroscientific "T" Series Pressure
Transducer Instruction 30
Coeff. Value Entry
U
0
5.860253 5.8603
Y
1
-3970.348 -3970.3
Y
2
-7114.265 -7114.3
* Y
3
102779.1 102.78
C
1
70.29398 70.294
C
2
6.610141 6.6101
C
3
-119.2867 -119.29
* D
1
0.0308837 30.884
D
2
0.0 0.0
T
1
26.33703 26.337
T
2
0.8516985 0.85170
T
3
21.80118 21.801
T
4
0.0 0.0
T
5
0.0 0.0
* Y
3
and D
1
coefficients are entered as Y
3
/1000
and D
1
*1000.
Only the first 5 digits of each 7 digit coefficient
are entered in the datalogger. The maximum
error that occurs due to using five digit
coefficients is 0.001 psi throughout a 15 psi
range at any temperature between -30 and
+60
°C. The maximum error in temperature
calculations is 0.2
°C over the same temperature
range.
CONNECTIONS
Figure 7.17-1 details the components required
for connecting the transducer to the CR10X.
The user supplied components are commonly
available at commercial electronic stores.