Code and schematic for 4-20mA current loop tester (PICAXE)

DrWhoF · Apr 4, 2006

I need a 4-20mA loop tester.
Any ideas are appreciated.

vsgiri · Apr 4, 2006

4 20ma tester

Hi DrWhof!

Use a terminating resistance of around 560 ohms , and use a dc ammeter to calibrate your 4-20mA loop for:
1. Line regulation : Vary the input voltage for a constant load and
2. Load Regulation : Vary the load for a constant input voltage.

Check the extremities of process measurement in both cases.
Hope it answered your question!

Giri

Miguel Gaspar · Apr 4, 2006

4 20 ma tester

Firs question analog or digital?

IanP · Apr 5, 2006

4-20ma loop tester

I have come across a nice little circuit based on the PICAXE-08M .. it is 4-20mA current loop tester ..
So, without any further comments, take a look at the attached circuit and its description ..

Regards,
IanP

IanP · Apr 5, 2006

4-20ma tester circuit

Attached is the code for 4-20mA project ..

Regards,
IanP

DrWhoF · Apr 5, 2006

4-20ma current loop tester

I have PICAXE18X. Will this code work without changes?

IanP · Apr 5, 2006

4 - 20 ma tester

Besides their physical sizes (number of pins and program memory) there are also small differencies in the BASIC commands ..
However, I can't see any reason why the PICAXE-18X couldn't be used in this application ..
Just verify the names of inputs and outputs and you shoud be fine ..

Regards,
IanP

IanP · Apr 7, 2006

4ma to 20ma tester

This software uses "pin3" as the push-button (reset) input and PICAXE-18-X doesn't have "pin3" .. see picture below ..
You will need to change it to, say, pin2 (other options are: 0, 1, 6 and 7) ..

Regards,
IanP

DrWhoF · Apr 7, 2006

4-20ma testers

"pin2" you mean physical pin 1 as In2, correct?

IanP · Apr 7, 2006

lm317 4-20ma

That is correct, pin2 = IN2 (ICs pin 1) ..
Also make sure that you connect the remaining inputs/output used in this project to the relevant PICAXE-18X pins ..

Regards,
IanP

DrWhoF · Apr 8, 2006

looptester 4-20ma

PICAXE-08M circuit has 5V voltage regulator.
In my test circuit I use 3x1.5V batteries.
Software uses some values for 4, a2 and 20mA. Are they related to 5V supply?

IanP · Apr 9, 2006

cheap 20ma tester

The numbers you mentioned have been selected with the reference to 5V supply ..

PICAXE analoge inputs are referred to +V supply .. see picture below .. therefore you should use +5V as your power supply, and the best thing to do is to select 78L05 voltage regulator with the output voltage as close to 5V as possible, or employ adjustable regulator such as LM317(L) and adjust the voltage to 5.00V ..

Regards,
IanP

DrWhoF · Apr 10, 2006

adjustable 4 to 20ma tester

I have this circuit running but with some problems.
It starts with 4.9mA and after the reset button is pressed goes up to 12.9mA and further to 21.0mA then back to 0mA and LED flashes.
The same situation repeats each time I press button.
Why it does not start from 4.9mA up to 21mA and back to 4.9mA and so on?

How can I calibrate current from 4.9-21 to 4-20mA?

IanP · Apr 11, 2006

voltage regulator 4-20ma circuit

Software bugs ..

In LOOP0 change the value from 444 to 244 ..

In FREEZE, after the line:
if w3<70 ...
add:
if w3<45 then tweakup

With these changes implemented, after initial 4mA (or so) - on power on - when you press the button PICAXE should start the cycle and the sinking current should rise to 12mA (or so), wait a while, and rise to 20mA (or so) and the fall down back to 4mA (or so), wait a while and continue the cycle ..

As far as calibration is concerned, w4 is responsible for the current levels:
w4=80 for 4mA
w4=244 for 12mA
w4=408 for 20mA
If these values do not match try to change them +/- as much as required ..

Regards,
IanP

DrWhoF · Apr 11, 2006

picaxe 4-20ma transmitter

Thank you so much for your help.
I modified 2 of 3 of values and now I have 4mA, 12mA and 20mA.
After I press the start button the circuit start cycles and one cycle take about 40s.
IanP, once again thank you very much.

dika · Jun 15, 2006

4-20ma signal loop tester

any alternative beside using PICAXE? it's rather hard to find it in my area. perhaps 8051 or AVR?

IanP · Jun 15, 2006

lm317 4 20ma

This project can be realized with any microcontroller, especially ones with ADC block and PWM module build-in ..
PICAXE has all of the above plus it is extremely easy to program (BASIC) ..
Try to find out if there is a distributor somewhere near you .. the list of international distributors is available at:
**broken link removed**

Regards,
IanP

jjohn · Jun 23, 2006

buy 4-20ma tester

Simplest and Cheapest is Multimeter Analog / digital

liux1998 · Sep 11, 2007

4 20ma circuit test

You cab buy a multimeter with 4-20mA output.

romarlo · Oct 23, 2013

i am very interesting in the 4-20ma loop tester, i want make a portable tester is it posible?

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Code and schematic for 4-20mA current loop tester (PICAXE)

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