YSI WaterLog Series, Owner'S Manual

Page: 94 / 174

4-20mA Out
The 4-20mA Output is found at the end of the bottom row of ports, next to the Analog ground
channel (Agnd) on the front panel of the System 5000
. Using the 4-20mA Output, the System
TM
5000 can be set up to generate a current output simulating a 4-20mA sensor. The System
TM
5000 does not actually generate the current in the loop but controls the current in a loop that is
TM
externally powered. The 4-20mA connection points are optically isolated from the rest of the
circuitry.
Min: This is the minimum value to expect from the Task’s Input. For example, if a temperature
probe was being measured and had a range of -50 to +50 degrees, the Max level would be set to
50 and the Min level set to -50. With this setup, a temperature of -50 would cause a milliamp
output of 4.00 milliamps and +50 degrees would produce a 20.0 milliamp output.
Max: This is the maximum value to expect from the Task’s Input.
Note that as the range is enlarged the resolution of the output current is decreased, and the
opposite if the range is reduced. The resolution is calculated as:
(mA Output Range) / (Input Range) = mA per Input Unit Change.
In the above example, presuming the temperature probe produces only integer values:
(20 - 4) / (50 - (-50)) = 16/100 = 0.16mA per degree change.
6-36 Outputs
System 5000
TM