CR300-Series Datalogger
26
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
Typical Data Table
(p. 24)
, shows the average of the measurements taken over the minute beginning
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.
6. Details
6.1 Analog Measurements
Analog sensors output a continuous voltage or current signal that varies with
the phenomena measured.
6.1.1 Voltage Measurements – Details
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
RMS
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
N1
.
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.
6.1.1.1 Single-Ended Measurements
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:
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