
SmartReader Data Loggers
44
Copyright © 2010 ACR Systems Inc. All Rights Reserved.
4,000 * 20 - 10,000 = 70,000 ohms
Figure 7-5: Modifying the 2.5 volt channel
Since you will not always be able to get the exact resistor value that you calculated, you can
determine the actual input range you will have by plugging the value of the resistor back into
the formula:
Ein = R + 10,000 / 4,000
This value will be needed when it comes time to create your own custom equation using
TrendReader software.
You can easily convert the 2.5V channel to measure 0 to 25 mA current by wiring a 100 ohm
resistor between the "2.5V" and "-Common" terminals.
200 millivolt Channel
The 200 millivolt channel can be modified to span higher ranges (greater than 200 mV DC) by
also adding two resistors, in the same way as shown for the 2.5V channel in Figure 7-5. The
value of the resistor marked "10k" must be 10,000 ohms ±1% or better. The value of the
resistor (R) can be calculated by the following formula, based on the desired voltage input
range (Ein):
R = 50,000 * Ein - 10,000
You can also modify the 200 mV channel to log current loop signals with greater sensitivity
than the two 25 mA channels. Put a 100 ohm resistor across the "200mV" and "-Common"
terminals and you will be able to log currents from 0 to 2.0 mA with approximately ten times
the resolution of the 25mA channels. The equation to use to determine other current (Iin)
ranges, in milliamps, is:
R = 200 / Iin
Comentarios a estos manuales