Yokogawa 415 Steam and Gas - Manual (Page 42)

4.1.1 Load Specification
Maximum load which the output can drive:
Internally powered loop: 500 ohms
Externally powered: R = (V-5)/.02
where V is the external loop voltage
R is the maximum load in ohms.
Output impedance of 0-10 Volt source: 100 ohms
4.1.2 Calculation
Parameters relating to this option are programmed when calibrating the
instrument (see section 5) and provide for:
Defining the rate which is equivalent to 4mA or 0 volts.
Defining the rate which is equivalent to 20mA or 10 volts.
Selecting the output range as 4-20mA (which also gives 2-10 volts on
the voltage output circuit) or as 0-10 volts (which gives 0-20mA on the
current output circuit).
By being independently able to set the output range, the instrument can
effectively be programmed to amplify the input signal. In driving chart
recorders, for example, this enables the output to zoom in on a particular
operating area, instead of having to display the full operating range of the
transducer.
For example, 4mA may be set as 0 kg/min and 20mA as 200 kg/min. However,
the user could set 4mA as representing 100 kg/min and 20mA as representing
120 litres/min.
For rates or displayed values above and below the maximum and minimum
values the output will remain at its 20mA or 4mA level respectively.
It should be noted that the output will be updated every 0.5 seconds in unison
with the display and, between updates, the output value is constant.
40 Options