ACR Electronics SmartReader Plus Reference Manual page 63

Since you will not always be able to get the exact resistor value that you calculated, you can
determine the logger's actual input range by plugging the value of the resistor (R) you obtain
back into the equation. For example, if the closest resistor you could obtain was 1.05M ohms,
then the actual voltage input range would be:
This value will be needed when it comes time to create your own custom equation using
TrendReader software.
You can also easily convert the 10V channel to measure 0 to 100mA current simply by putting
a 100 ohm resistor (minimum rating: 2 watts) between the "10V" and "Common" terminals.
5 Volt & 2.5V Channels
The 5 volt and 2.5 volt channels can be modified to span higher ranges (greater than 5 and 2.5
volts DC respectively) by adding a single resistor, in the same way as shown for a 10V
channel in Figure 7-3 to the "5V" and "2.5V" terminals. The value of the resistor (R) can be
calculated by the following equations, based on the desired voltage input range (Ein). A final
Range can be determined to write a custom equation in TrendReader software.
Terminal
200mV Channel
The 200mV channel can be modified to span higher ranges (greater than 200mV DC) by
adding two resistors to the input terminals as shown in Figure 7-4. The value of the resistor
Copyright © 2010 ACR Systems Inc. All Rights Reserved.
Ein = (R + 1,020,000) / 102,000
(1,050,000+1,020,000) / 102,000 = 20.29V
Figure 7-3: Extended Voltage Range on 10V Channel
Resistor (R)
5 V R = 202,000 x Ein - 1,010,000
2.5 V R = 408,000 x Ein - 1,020,000
SmartReader Plus Data Logger
Range
Ein = (R + 1,010,000) / 202,000
Ein = (R + 1,020,000) / 408,000
54