Details; Analog Measurements; Voltage Measurements - Details; Single-Ended Measurements - Campbell CR300 Series Operator's Manual

CR300-Series Datalogger
6.

Details

6.1

Analog Measurements

6.1.1 Voltage Measurements – Details

6.1.1.1 Single-Ended Measurements

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Subsequent rows are called data records. They include observed data and
associated record keeping. The first field is a timestamp, and the second field is
the record number.
The timestamp shown represents the time at which the data is written.
Therefore, because the scan rate of the program MyTemperature.CR300 is 1
second, Temp_C_Avg in record number 3 in TABLE 5-2, Typical Data Table
, shows the average of the measurements taken over the minute beginning
(p. 24)
at 14:26:01 and ending at 14:27:00. As another example, consider rainfall
measured every second with a daily total rainfall recorded in a data table
written at midnight. The record timestamped 2016-03-08 00:00:00 will contain
the total rainfall beginning at 2016-03-07 00:00:01 and ending at 2016-03-08
00:00:00.
Analog sensors output a continuous voltage or current signal that varies with
the phenomena measured.
Sensor connection is to H/L terminals, which are configurable for differential
(DIFF) or single-ended (SE) inputs.
• Maximum input voltage range: –100 to +2500 mV
• Measurement resolution range: 0.33 to 33 µV
Voltage measurements are made using a 24-bit A-to-D converter. A high-
impedance programmable-gain amplifier amplifies the signal. Internal
multiplexers route individual terminals within the amplifier. The CRBasic
measurement instruction controls the A-to-D converter gain and configuration
– either single-ended or differential input.
A voltage measurement proceeds as follows:
1. Set amplifier gain for the voltage range selected with the CRBasic
measurement instruction parameter Range. Set the A-to-D converter for
the first notch frequency selected with f
2. If used, turn on excitation to the level selected with ExmV.
3. Multiplex selected terminals (SEChan or DiffChan).
4. Delay for the entered settling time (SettlingTime).
5. Perform the A-to-D conversion.
6. Repeat for input reversal as determined by parameter RevDiff.
7. Apply multiplier (Mult) and offset (Offset) to measured result.
A single-ended measurement measures the difference in voltage between the
terminal configured for single-ended input and the reference ground. For
example, single-ended channel 1 is comprised of terminals SE 1 and ⏚. Single-
ended terminals are labeled in blue. The CR300 has six SE terminals. The
single-ended configuration is used with the following CRBasic instructions:
RMS
.
N1