Campbell CR800 Series, Руководство оператора

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Section 8. Operation
349
input or differential input. Internal multiplexers route individual terminals to the
PGIA.
Timing
(p. 150)
of measurement tasks is precisely controlled. The measurement
schedule is determined at compile time and loaded into memory.
Using two different voltage-measurement instructions with the same voltage
range takes about twice as long as using one instruction with two repetitions.
See table Parameters That Control Measurement Sequence and Timing
(p. 350).
FIGURE 80: Programmable Gain Input Amplifier (PGIA):
H to V+, L to V–, VH to V+, VL to V– correspond to
text.
A voltage measurement proceeds as follows:
1. Set PGIA gain for the voltage range selected with the CRBasic measurement
instruction parameter Range .
2. Turn on excitation to the level selected with ExmV .
3. Multiplex selected terminals (
InChan
) to the PGIA and delay for the entered
settling time ( SettlingTime ).
4. Integrate the signal (see Measurement Integration
(p. 350)
) and perform the A-
to-D conversion.
5. Repeat for excitation reversal and input reversal as determined by parameters
RevEx and RevDiff .
6. Apply multitplier ( Mult ) and offset ( Offset ) to measured result.
See Basic Voltage Measurements — Specifications for measurement speeds.
The CR800 measures analog voltage by integrating the input signal for a fixed
duration and then holding the integrated value during the successive
approximation analog-to-digital (A-to-D) conversion. The CR800 can make and
store measurements from up to three differential or six single-ended channels
configured from H/L terminals at the minimum scan interval of 10 ms (100 Hz)
using fast-measurement-programming techniques as discussed in Measurement:
Fast Analog Voltage
(p. 233).
The maximum conversion rate is 2000 per second (2
kHz) for measurements made on a one single-ended channel.