Campbell Scientific CR510 Basic Datalogger - Manual (Page 80)

SECTION 7. MEASUREMENT PROGRAMMING EXAMPLES
7-2
CR510
FIGURE 7.2-1. Typical Connection for Active Sensor with External Battery
Ground at the LI-6262 is 0.065 V higher than ground
at the CR510. The LI-6262 can be programmed to
output a linear voltage (0 to 100 mV) that is
proportional to differential CO
2
, 100
µ
mol/mol full
scale, or 1
µ
mol/mol/mV. If the output is measured
with a single-ended voltage measurement, it is
0.065 V or 65
µ
mol/mol high. If this offset remained
constant, it could be corrected in programming.
However, it is better to use a differential voltage
measurement which does not rely on the current
drain remaining constant. The program that follows
illustrates the use of Instruction 2 to make the
measurement. A multiplier of 1 is used to convert
the millivolt output into
µ
mol/mol.
PROGRAM
01: Volt (Diff) (P2)
1:
1 Reps
2: 25
±
2500 mV 60 Hz Rejection
Range
3: 1 DIFF Channel
4: 1 Loc [ umol_mol ]
5: 1 Mult
6: 0 Offset
7.3 HMP45C TEMPERATURE AND RH
PROBE
Instruction 11 (107 Probe) is used to measure
the temperature portion of the HMP45C Probe.
It makes a single ended voltage measurement,
and calculates temperature with a fifth order
polynomial. A multiplier of 1.0 and offset of 0.0
yields temperature in degrees Celsius.
Instruction 4 is used to measure relative
humidity. It provides an excitation voltage to
power the RH sensor. A 150 millisecond delay
is allowed for warm-up before the single-ended
measurement is made.
The probe has an output of 0 to 100 millivolts
for the 0 to 100% RH range, a multiplier of 0.1
and an offset of 0.0 provides relative humidity in
percent.
This example uses Control Port 1 to power the
RH sensor.
CONNECTIONS
The HMP45C probe is measured by two single-
ended analog input channels. The green (RH)
and the orange (temperature) leads are
connected to either a HI or LO input. The black
thermistor excitation lead connects to any
excitation channel. The yellow lead powers the
RH sensor via control port 1. The white and
purple leads connect to Analog Ground (AG).
The clear lead is the shield which connects to
Ground (G) on the CR510.
01: Temp (107) (P11)
1:
1 Reps
2: 1 SE Channel
3: 1 Excite all reps w/E1
4: 1 Loc [ air_temp ]
5: 1.0 Mult
6: 0.0 Offset