Friday, October 05, 2018

RTD 3-W Mains Power 4-20 mA Transmitter

This is the Photo of a RTD 3-W Mains Powered Temperature 4-20mA Transmitter. The Circuits and PCB are here RTD PT100 Transmitter and Multiplexer.The Circuit RTD-Pt-100-Transmitter.

We can classify Transmitters as shown below. The Measured Parameter Temperature, Flow or Events Has to reach an Intelligent Data Storage and Analysis System. It may just be an Human Operator who jots the data on a Notepad and Turns a Few Dials based on his Experience or an embedded controller. It could even be a Computer Network or a Web Application used,

RTD PT100 Transmitter and Multiplexer PCB
  • Analog Transmitters - Like 4-20mA Loop.
  • Electrically Isolated Analog Transmitters.
  • Transmitters that need to be Intrinsically Safe.
  • Digital Transmitters and Optical Interface.
  • Wireless Transmitters and TCP-IP.
The job of the transmitter is to take the weak analog measured parameter information from sensor, be close to it, amplify, clean, linearize the signal if required and send strong - error free data over a long distance to an operator or system.

Process Control Instruments and Custom Solutions has been my core Strength. The RTD Pt-100 Transmitter with 4-20 mA output shown here was used in numbers with a 4-20 mA Analog Multiplexer. This was in turn monitored/controlled by a PLC SCADA System to monitor many points in a large Industrial Plant. The external multiplexer makes unlimited channels possible with a Standard Analog Input and Digital Output Module.

Friday, July 27, 2018

Voltmeter Attenuator Rectifier

Measurement of Voltage : - In testing electronic circuits, Measurement of voltages is important for diagnosing faults and making the circuits work. In circuit diagrams given in equipment manuals, voltages at various points in the circuit are usually marked. A deviation from these values indicates that some component has failed and eventually leads to clues for isolating the faulty areas.

Voltage  measurement attenuator amp

Voltmeter Attenuator Rectifier

Specifications :-

D.C. Voltage
Ranges : +/- 200 mV, 2V, 20V, 200V, 2000V.
Input impedance: 10 mega ohms.
Circuit protection: + 2000V D.C. all ranges.
Over range: 100% to 1999.
Accuracy: +/- 0.5%.
A.C. Voltage
Note: Average responding Ranges calibrated for sine wave.
Ranges: 200 mV, 2V, 200V, 2000V
Input impedance 10 mega ohms.
Circuit protection : 750V r.m.s., all ranges.
Over range: 100% to 1999.
Description :-
As our DPM is capable of measuring only 200 mv full scale deflection, the input voltage in the case of exceeding the range needs scaling down. This is achieved by an attenuator chain.

Wednesday, July 18, 2018

Ammeter and Precision Rectifier

Studying current measurement is a prerequisite for many of the measuring techniques. The current parameter mainly specifies the power consumption in a circuit, given the value of resistance.

Current Shunt Amplifier digital control

It is found convenient to measure current rather than voltage for knowing power output and determining efficiency. It may be required to measure leakages in circuits at certain times. Hence the measurement of current constitutes a priority.

Ammeter and Precision Rectifier
Measurement of DC Current -

The circuit diagram for the measurement of current (d.c. and a.c. modes) is shown aside. For measurement of current switch SI is operated. The switch S-ad is kept in d.c. mode. This enables the current to pass through a shunt circuit consisting of resistors R26, R27, R28, R29 and R 30. The current ranges are provided in 5 decades i.e. 200 micro-amps, 2 milli-amps, 20 milli-amps, 200 milli-amps and 2 amps. An additional current range that can be read upto 20 Amps is also provided. However, for measuring this high current the green terminal provided on the meter should be used. When a current to be measured is fed to the input terminals of the instrument appropriately, a voltage proportional to the current through the shunt resistor is fed into the DPM which measures the d.c. voltage which in turn indicates the d.c. current being fed.

Test and Measurement Instruments

Measurement of AC Current -

In case of a.c. measurement, the switch S-ad is kept in a.c. mode. The a.c. current path is similar to the d.c. current path in the shunt resistor. However the voltage tapped across the shunt resistor is fed into IC2 which is a buffer. The output of IC2 is fed to IC3 through capacitors C10 and C11. This IC is an operational amplifier acting as a precision rectifier. The output of IC3 is fed to the input of the DPM for measuring the a.c. current being fed to the input terminals. It can be seen that the current measurement is similar to the voltage measurement except that the attenuator chain is replaced by the shunt resistor circuit.

(This is scanned-ocr from my earlier file, some mistakes corrected - delabs)

Circuits by Application

Analog Circuits

  1. Battery Level Indicator
  2. Simple Sample and Hold
  3. Sample and Hold Standby
  4. Voltmeter Attenuator
  5. Precision Current Source
  6. Opamp Supply Virtual Ground

SCR and Triac

  1. Solid State Relay
  2. Normally Closed AC SSR
  3. AC-AC-SSR
  4. DC-DC SSR
  5. 2N2646 based Pulser
  6. Drive SCR thyristor

Mains Power

  1. Flashing Neon Lamp
  2. Dimmer power control
  3. Edison Bulb Life Extend
  4. Mains Current LED
  5. Mains Voltage LED

Digital Circuits

  1. Simple Digital Counter
  2. Running Lights
  3. Frequency Divider
  4. Crystal Oscillator
  5. Simple High speed switch
  6. Differential TTL converter

Measureall DMM

  1. Ohmmeter Measure Resistance
  2. Precision Digital Attenuator
  3. Precision Amplifier

Mixed Circuits

  1. Monostable Multivibrator
  2. Digital to Analog
  3. LM311 Oscillator
  4. PLL using 4046
  5. VCO with LM331
  6. BCD Thumbwheel to Analog
  7. V to F Converter ICL8038
555 Circuits
  1. OR gate with two 555
  2. fixed frequency duty cycle
  3. Pulse width modulation
  4. Astable Multivibrator
  5. uC Reset Generator
  6. LM555 Voltage Doubler
  7. 555 Power Oscillator
Discrete Circuits
  1. Isolated dual supply
  2. Sound to light converter
  3. Water operated relay
  4. Telephone Indicator
  5. Passive volume control
  6. RS232 Opto-Isolation
  7. Voltage Level Indicator
  8. Relay Driver
  9. Constant Current LED
  10. Voltage Doubler
  11. FET Current Source
Opamp Circuits
  1. Three Opamp Differential
  2. Two Opamp Differential
  3. Buffer Opamps
  4. Differential Op-Amp
  5. Inverting Opamp
  6. Non Inverting Opamp
  7. Digital gain control
  8. Square Triangle Oscillator
  9. Dual Polarity Output Amps
  10. Ammeter Precision Rectifier
  11. Voltage / Current 4-20 mA
  12. Current Source for RTD
Power Electronics
  1. Dual Power Supply
  2. Single Power Supply
  3. Battery Backup Supply
  4. 5V 1A Supply LM2575
  5. 5V Power Supply L296
  6. Dual Power Supply
  7. Tubelight Electronic Choke
  8. Voltage Doublers Multipliers
  9. White LED Lamp on Ni-Cd

uC and uP

  1. PC RS232 with MAX232A
  2. Battery Backup SRAM
  3. watchdog uC uP systems
Instrumentation Circuits
  1. Mains monitor LM3914
  2. Simple Mains monitor
  3. single digit voltmeter
  4. High Resistance Meter
  5. Diode Thermometer
  6. Function Generator
  7. Diode Leakage Tester
  8. Analog LED Ohm Meter
  9. Millivolt Source Current Loop
Process Control
  1. AD590 - temperature
  2. Thermocouple Amplifier
  3. Linearizing Thermocouple
  4. Thermocouple Amplifier
  5. 0-1V to 4-20 mA
  6. 1-5V to 4-20 mA
  7. InfraRed - Optical Switch
  8. InfraRed Detector

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