Xylem H-4280 - Manual (Page 10)

2-2 Installation And Maintenance
H-4280
2.3 +5Vref Output
The H-4280 has a precision 5.00V excitation output terminal for powering potentiometers, thermistors and
other sensors. The +5Vref terminal is internally connected to the A/D converter. Measurements made with
resistance sensors powered from the +5Vref terminal will be “ratio metric” in that errors in the absolute
value of the reference cancel out. The +5Vref output is normally turned off to save power while the
module is in its sleep mode and is switched on before a measurement is made. The “warmup time” is a
programmable delay (1 to 999 seconds) which elapses before the first measurement is made If desired, the
excitation output can be programmed to remain active while the module is asleep. The +5Vref terminal is
for powering potentiometers, thermistors and other low current senors. Do not draw more than 50mA from
the +5Vref terminal.
The warmup delay is configured with the extended “aXRWT!” and “aXWWTnnn! commands. The
+5Vref power mode during sleep is configured with the extended “aXRPM!” and “aXWPMnn! commands.
See Chapter 3 for details.
2.4 Averaging
The H-4280 can make up to 700 measurements/second (per 8-channels) The module makes multiple high
speed measurements, averages the results and reports one measurement per channel. The number of
samples can be programmed from 1 to 65535, the H-4280 comes from the factory configured to make 100
samples for each channel (100 x (1/700)=0.142 seconds ). The number of samples per measurement (1-
65535) is the same for all 8-channels. This setting is configured with the extended “aXRMC!” and
“aXWMCnnn! commands. See Chapter 3 for details.
2.5 Channel Settings
Each channel can be configured to make Unipolar/Bipolar and Single/Differential measurements.
Unipolar 0 to 5.0 Volts (resolution is 1.2mV)
Bipolar: ±5.0 Volts (resolution is 2.4mV)
Single: Measurement is referenced to ground
Differential: Measures the difference between two adjacent input channels
These and other settings are configured with the extended “aXRCn!” and “aXWCn! commands. See
Chapter 3 for details.