Showing posts with label Process-Control. Show all posts
Showing posts with label Process-Control. Show all posts

Tuesday, January 17, 2017

RTD and Connections - Mini 3W 4-20mA transmiter

I´ve been looking at the mini-three wire 4-20mA transmitter and it is everything I need to try a new way of measuring the temperature. It is great but there are a few questions about it I hope you can answer them:

- What is the meaning of RYIN and RXIN?

- You say that it is a three wire circuit but I can only seen two points of connection for the PT100. Is it because the signal conditioner of the three wire PT100 isn´t drawing?

- The OUTPUT connector is where I can find the 4-20 mA?

I hope there is no problem to answer these quetions to me, I would be really pleased if you can do it and I´d appreciate it.

Many thanks and hope to hear soon from you.

Mail from AD - Spain

All the transmitter circuits can be seen here. Industrial Process Control Circuits

RTD and Connections - Mini 3W 4-20mA transmiter

As this circuit was popular i have made a separate page for it. Mini RTD Pt-100 Three Wire Transmitter

A ex-customer of mine, (ex because i don't manufacture now.) wanted a low cost transmitter, so i made this.

What is the meaning of RYIN and RXIN? - Connect it to any two wire RTD

For RTD read more RTD Omega - RTD Intro

You say that it is a three wire circuit ....

+V .... -V .....OUTPUT ...... on the left are the three wires.
+V and -V is the Supply. OUTPUT is a Current Sink Directly Proportional to Temperature on RTD.

In the Costlier 2 Wire systems, Current Drawn by Transmitter is Directly Proportional to Temperature on RTD. Two wire systems can be just looped, 3 Wire like mine has to be wired, more wire.

The OUTPUT actually drinks 4-20mA prop to Temp. Put a Ammeter (fused) in 0.2A range in Series with a 50 Ohm Resistor. Black Lead of ammeter to this OUTPUT. Red Lead to one end of 50 Ohm. The other End of 50 E to +V.


Thank you for your quick answer. I think I´ve got it. Although there is another question that has come up to me while reading your email. +V and -V is the supply I apply to the PT100? I am applying 24DCV so I suppose the +V is the 24V and -V is the ground, isn´t it?

Reply from AD

YES - +V is the 24V and -V is the ground, anything above 12V will work.

The 24 V should be applied to +V and -V only. Not to RTD Directly. RTD Directly Connected to 24V will BURN the RTD.

RTD is a Thin Platinum Film or Wire of 100 Ohms worth. The Resistance varies with temperature.

A 1mA ONLY Constant Current is sent thru the RTD to measure the Voltage across it. From the measured voltage 100mV for the 100 Ohms is subtracted using opamps.

The balance mV is Directly Proportional to Temperature. This mV is converted to 4-20 mA. 4-20 mA is a Strong Signal for Current Loop Transmission.

4mA is 0% 12mA is 50% and 20mA is 100% of the range you calibrated.

Related Reading

Thursday, October 06, 2016

SCADA System - Project Idea

I am a student of Electronics and Instrumentation Branch from BP. I am doing my training at ..... where i have been assigned a project to implement SCADA System using Microcontroller.

Right now,i have a good knowledge of PSOC and AVR microcontrollers but since i am new to this technology,i am not getting how i should proceed for the project.i would be greatful to you if you can provide some information about the previous projects students have done in you organization regarding scada implementation.

from MG

A "SCADA System" may consist of a Human using a Computer with Special Software Overseeing a Process Control System made of many sensors, transmitters, autonomous controllers and actuators made of motor drives and heaters.

SCADA System has a Computer, sometimes Network, HMI, PLC Control Panel, Secondary Slave Instruments. Autonomous Process Control in Remote areas and Protection and Fallback Units.

SCADA System

SCADA – Supervisory Control and Data Acquisition

Some of these elements may send data to the computer which may Analyze and Indicate the condition of process or progress. The Human Operator can then fine tune the parameters of his system or study and record process cycles for quality and yield.

You discuss this with your mentor and then build a part of it, or implement a part of it in an existing system. A whole SCADA system is too big a project, but a simulated or demo software interface project can be made.
This will be posted comment on that post to continue. Any other doubt post as a comment, .


Wednesday, September 17, 2014

Temperature Meters with Analog Recorder Output

I would like to know if you offer a monitoring solution that will constantly measure ambient (air) temperature (say, 0 to 150°F), and provide a corresponding DC voltage output of either 100 mV, 1 V, 5 V, or 10 V. Do you make a unit that can be configured to do this?

Mail From JPE - WV - US

Analog outputs were very popular as they are inputs to Strip Chart Recorders, Later they had an extra use for PC Based Data Acquisition, data Loggers and PLC. Now we have Instruments with digital and wireless outputs too.

Temperature Meters - DP116 - Omega
Economical 3/64 DIN panel meter that has a full size 0.56" green or red LED display, with a built-in analog output and display hold capability. 3 1 /2 Digit Display.

Features Include
  • Thermocouple and RTD Input
  • Full-Size 0.56" (14.2 mm) LED Display
  • Analog Output Standard
  • 1 /8 DIN Panel Adaptor Standard

Economical Digital Meters DP18 - Omega

Economical Digital Meters DP18 - Omega

The DP18 series is a complete family of panel meters with input cards for voltage, process and temperature measurement and control. The signal conditioners for voltage will measure ac or dc voltages or true RMS.

Modular Design, Options for Alarms, Analog Output of Communications, 3 1/2-Digit LED Available in Red or Green Displays


Sunday, June 22, 2014


I am working on alarm systems and would like assistance in designing wireless link for the unit, ie sensors to control panel, control panel to monitoring station.

I noticed most of the circuits available on your sites are FM 88 - 108 MHz, which would definitely cause interference. Can you please assist me with this final part of my system.

mail from RT

i would like to know........... The wireless link distance of Transmitter and receiver. The frequency range you want like FM 'n' MHz Are you aware of the regulations of wireless transmission.

What band is allowed in your country and what distance. what type of data needs to be transmitted. If this is for process control, RF should be avoided if possible. You should use 4-20mA current loops, RS485 or IR optics.


You can study these pages ...........

Wireless Transceiver with Modbus Interface at Omega 

Omega Modbus Wireless Transceiver

"The OMWT-XREC-MOD Wireless Transceiver uses an embedded 100-milliwatt frequency hopping wireless modem that provides communication between a local RS-485 network and a remote network of RS-485 connected devices. The OMWT-XREC- MOD will automatically sense the direction of data flow and switch the RS-485 and radio devices accordingly."

Read more here Modbus Communication Protocol Suite

with a RS485 and Modbus Network you can do it.