CR10X User Guide
7-14
Program
01: Full Bridge (P6)
01:
1
Rep
02:
31
2.5mV 50Hz rejection Range
03:
3
IN Chan
04:
1
Excite all reps w/EXchan 1
05:
2500
mV Excitation
06:
11
Loc [:Rs/Ro ]
07:
0.001
Mult
08:
.02344
Offset
02: BR Transform Rf[X/(1-X)] (P59)
01:
1
Rep
02:
11
Loc [:Rs/Ro ]
03:
50
Multiplier (Rf) =R1/R0
03: Temperature RTD (P16)
01:
1
Rep
02:
11
R/Ro Loc Rs/Ro
03:
12
Loc [:TEMP C ]
04:
.98214
Mult
05:
0
Offset
7.12 Pressure Transducer – 4-Wire Full Bridge
This example describes a measurement made with a Druck PDCR830 depth
measurement pressure transducer. The pressure transducer was ordered for use
with 5V positive or negative excitation and has a range of 350mbar or about 3.5m
of water. The transducer is used to measure the depth of water in a stilling well.
Instruction 6, 4-Wire Full Bridge, is used to measure the output of the pressure
transducer. The high output of the semiconductor strain gauge necessitates the use
of the 25mV input range. The sensor is calibrated by connecting it to the CR10X
and using Instruction 6, an excitation voltage of 2500 mV, a multiplier of 1 and an
offset of 0, noting the readings (*6 Mode) with 10cm of water above the sensor
and with 334.6cm of water above the sensor. The output of Instruction 6 is 1000
V
s
/V
x
or millivolts per volt excitation. At 10cm the reading is 0.19963mV/V and
at 334.6 cm the reading is 6.6485mV/V. The multiplier to yield output in cm is
therefore:
(334.6 - 10)/(6.6485-.19963) = 50.334 cm/mV/V
The offset is determined after the pressure transducer is installed in the stilling
well. The sensor is installed 65cm below the water level at the time of installation.
The depth of water at this time is determined to be 72.6cm relative to the desired
reference. When programmed with the multiplier determined above and an offset
of 0, a reading of 65.12 is obtained. The offset for the actual measurements is thus
determined to be 72.6 - 65.12 = 7.48cm.
The lead length is approximately 3m, so there is no significant error due to lead
wire resistance.