PicoLog Self-Help Guide
AR346-1
© Copyright 2014 Pico Technology Ltd.
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laptop. Files can be exported as .txt or .csv for loading into Microsoft Excel or other
spreadsheet application.
Here are some instructions on how to setup for 4–20 mA operation with an example of a
0 to 10 bar pressure sensor:-
All you have to do is to pass the 4–20 mA current output by the sensor through a 120 Ω
resistor to generate a voltage varying from 480 mV to 2400 mV. The resistor is best
placed in parallel with the input terminals of the PicoLog 1012 (from the channel input
pin to ground). The 0 V terminal of the +12 V to 24 V sensor supply is connected also to
the ground of the 1012. The resistors used can be soldered to the terminal board
permanently or just gripped by the screws used to connect wires to the terminal board.
The positive output of the supply goes to the positive terminal of the sensor. The
negative terminal loops back to the other end of the 120 Ω resistor. Thus the sensor
current goes round in a loop through the sensor, resistor and supply.
Assuming you have connected up the sensor, resistor and supply as described above,
you just need to set the scaling for the channel in question. We will illustrate how to set
up channel 1 for 4–20 mA operation with graph scaling from 0 bar to 10 bar as an
example.
1.
Start PicoLog and set up your sample rates as required.
2.
When you get to the PicoLog 1012 measurements dialog, click Add.
3.
Type Pressure as the Name, select DC Volts and leave the Scan time as the
default 10 000 µs.
4.
Now click Options. (You might be asked to save the present setup. If so, click
OK.)
5.
In the Parameter Options dialog box tick Use parameter Formatting, and type bar
in the Units box. Field Width = 4, Decimal places = 2, Minimum value = 0,
Maximum value = 10. Now click Scaling to go to the next dialog.
6.
In the Parameter scaling dialog box, select Table Lookup as the Scaling method
and in the visible text box, type:-
0.48 0
2.4 10
This tells the program to equate 0.48 V to 0 bar on the graph and 2.4 V to 10 bar
on the graph.
The 0.48 is derived from 4 (mA) times 120 (Ω) = 0.48 V.
The 2.4 is 20 (mA) times 120 (Ω) = 2.4 V.
7.
Click OK to go back through the open boxes and channel A should now be scaled
from 0 to 10 bar.
If the sensor is not powered-up, the reading will be about –1.2 bar as that is the
equivalent reading for zero mA. (0 bar = 4 mA).
Look through the PicoLog manual for information on using PicoLog or click on the Help
button at any stage in PicoLog.