Resistance to Pulses Converter

riyajahamad

Member
Join Date
Jun 2002
Location
Pune-India
Posts
133
Hi PLC Experts,
Though this question not about PLC but related to it, expecting some suggestion from you experts.

I have application of checking Resistance for its values. Resistance to Pulses Converter will give pulses some connected to high speed counter of PLC. Resistance will compare with set value and PLC will decide OK or NOT OK. Right now same application is running in other machine but Resistance to Pulses converter is made locally & manufacturer no more in business. My questions are:

1) Is standard converter available to convert Resistance to Pulses?
2) What other options are available to such type of application other than analogue input card.

Thanks in advance.

Riyaz,
Pune India.
 
What I interpret from you us that you have a device that is giving resistance for it's position and you want to know that position in the PLC. That device has a range, what is it? Are you sure it's resistance and not current?

What is the specification of the device used to measure distance?
 
More information about the application is needed. The field device that measures is connected to some type of other field device that converts resistance to a PWM signal?
Rocksalt has the same confusion as I do..
Please describe your application (what is done ect...)
 
Last edited:
Application Explanation

Dear PLC Experts,
Thanks rocksalt & Bitmore for your response.
I will try to explain application:
My client manufacturer variable resistors (having 3-4 steps) which used in automobile to control wiper speed etc. To check it for correct resistance at desired step. Right now Omron CPM2A Sysmac and NT11S-SF121B is used. Step wise resistance setting done in HMI. Two local make converters are used first resistance is converted to voltage (0-10V) and voltage converted to pulses which is connected to first input of PLC. PLC is programmed such as it counts (High Speed Counter) pulses and compare with set values in HMI and give OK or NG of product.
My client is making new machine, I am unable to find converters which converters resistance to pulses and seeking help from you experts.
Hope this will help to understand my application.
Riyaz

 
I don't know of a unit that you could buy for a PLC, but I understand the electronics. The main part of the Resistance to Pulses converter is a Voltage to Frequency converter. A very good circuit is shown here built with a AD654 from Analog Devices. Some simple modifications are all that's needed to make it compatible for a PLC. You should be able to find many electronics shops in India that could design one for you, at very low cost.
 
PR electronics makes R/I transmitters (0-10K) and also make
I/F converters. This is all you need.
 
I also found the model 4222 from PRelectronics that converts
0-10K to 0-25 kHz (R/F converter)
 
You could also make your own R->P converter by using a NE555 timer circuit.


But I'll ask: Why convert ? Does the plc you are using not have an analog input to read the voltage ? Then switch to a different Omron plc that can read voltage.
 

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