These are the circuits and boards of a Mini Temperature Transmitter for a Platinum hundred ohms temperature Sensor.
The customer wanted a two wire system, this needs low power opamps which were ten times the price. If this transmitter works at 3mA it could have been two wire. Those parts were in short supply and the budget of customer was low. So i made it with regular opamps but three wire. The customer was satisfied as he got a cost effective solution. But now the situation of markets and products are different.
RTD Three Wire Transmitter
If you need to transmit the temperature from a high voltage area or toxic environment. You will need to hermetically seal the transmitters, convert the Voltage to frequency, frequency to IR LED flashes or RF. This can be then remotely monitored. Then the transmitter has to be battery-solar operated, low power too. ICL7135 is a simple solution. It has a serial output that can be used to Drive IR Leds. Remotely sense these flashes in a Micro-controller and you have a reading. You may be able to use optic-fibers too. Where volatile liquids are present so that the risks of sparks can be eliminated.
More at Process Control Circuits
This is the same Mini RTD Pt-100 Transmitter but in its case. Encapsulated in epoxy, hermetically sealed against harsh industrial environment. This will work well even near fumes of Ammonia with no corrosion. But not near vapors which can be ignited by sparking as terminals are still open. The side view shows zero and full scale ten turn bourns trimpots heads, for calibration. After cal it can be sealed with RTV compound.
Automation and Control is the predecessor of Robotics. A Jump Start, Practical and standard reference for Process Control is at at Omega Technical Reference.
A Control system is made of Sensors sending acquired data to a Controller which operates Actuators to manage the process in Real Time. Starting from a Bimetal Thermostat to a SCADA, the controller has grown from mechanical — electrical — analog — digital devices to microcontroller-computer based equipment.
Both in Control Systems and Robotics the Collaboration between Robots or Control Units, leads to the development of wireless network of Interactive, Intelligent and Distributed Self Governing Systems. The outcome is Web Process Automation, Web Applications based Solutions in Monitoring, Analyzing and Configuring these Sophisticated Networked Systems.
Read More at my – Industrial Process Control Applications
This is a RTD Pt-100 Transmitter, It can Convert Thermocouple mV or RTD mV to 4-20 mA Current Transmitter. The part numbers on Circuit and silk screen may not match. But the PCB may be usable. The output is a current source and not a current sink. It goes to a 4-20mA Mux with a common ground. The Circuit RTD-Pt-100-Transmitter Circuit.
This low-cost transmitter was made to send RTD information in a 4-20mA over long distance. The 4-20mA was the input to a Analog-Mux which interfaced to a GE-Fanuc PLC system and a 486 Computer. The Analog Multiplexer Built around CD4051 was was controlled by PLC to get data from numerous channels. This reduced the cost of the System. This is ok when Real-Time Acquisition is not required. The Analog 4-20 to 4-20 Mux-Buffer circuit can be seen at Industrial Process Control Circuits.
This was done as customer budget could not afford dedicated analog input modules for every channel. There were more than 50 Inputs. The thermal inertia of system did not need a real time or fast correction.
The PNGs of PCB is 600dpi 16 color. It is to be scaled appropriately.