Customizing Input Ranges - ACR Electronics SmartReader Plus Reference Manual

SmartReader Plus Data Loggers
53
1.10.4

Customizing Input Ranges

The standard input ranges on the SmartReader Plus 7 should be suitable for most process
signal applications but occasionally you may require measurement of non-standard input
levels where resolution is a primary concern. Ranges can be adapted easily by using either
one or two external resistors. TrendReader software has Equation functions that can be used
to scale the data to the new input levels.
The table below lists several possible input signal ranges and the recommended channels to
use. It also lists alternative channels that can be used for additional simultaneous monitoring
capability. These alternative channels will, however, require external resistors.
In the above table, the Range column lists examples of input signals that you may wish to
monitor using your SmartReader Plus 7. The Standard column lists the channel you would
normally choose to monitor that particular signal. The Alternative column lists other channels
that can be used to monitor the same input signals. In most cases, these channels will need
to be fitted with external resistors.
The resistor value that you will require to modify each SmartReader Plus 7 input channels is
selected by inserting your special input requirements into a simple equation. The following
sections detail these equations and the method of tying in these resistors.
10 Volt Channel
The 10 volt channel can be modified to span higher ranges (greater than 10 volts DC) by
adding a single resistor to the "10V" terminal shown in Figure 7-3. The value of the resistor
(R) can be calculated by following the formula below, based on the desired voltage input range
(Ein):
For example, if you wish to measure up to 20 volts, the resistor value should be:
NOTE: It is recommended to use resistors with a resistance tolerance of 1% or
better.
Range Standard
0 to 500 mV 2.5 V
0 to 1V 2.5 V
0 to 2V 2.5 V
0 to 3V 5 V
0 to 6V 10 V
0 to 20V 10 V
0 to 2mA 25 mA
4 to 20mA 25 mA
0 to 50mA n / a
0 to 100mA n / a
R = 102,000 x Ein - 1,020,000
102,000 x 20 - 1,020,000 = 1,020,000 ohms
Alternative
200mV
200mV
200mV
2.5V, 200mV
5V, 2.5V, 200mV
5V, 2.5V, 200mV
200mV
2.5V, 200mV
25mA, 5V
25mA, 10V
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