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Thermocoupler Circuits

Thermocouplers:  #'s - N      M - Z
 

Last Updated: October 18, 2017 05:04 AM

Circuits Designed by Dave Johnson, P.E. :

Alarm Sounds At Freezing Temperatures -  This electronic hobby circuit below is designed to activate a beeper alarm, whenever the outside air temperature is below 0 degrees C   (32F) .  A 9v battery powers the hobby circuit.  The average 9ua current is so low that the battery should last for many years . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Battery-Powered Freezer Alarm -  A typical freezer can contain hundreds of dollars with of food.  If the device becomes unplugged or if the door is left open too long, the food inside can quickly become spoiled.  The hobby circuit below is a battery powered alarm system, which is attached . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Freeze Alarm -  I chose an accurate thermistor from Keystone as the temperature sensor for this circuit.  This device has a very specific resistance at a particular temperature.  According to the data sheet for the thermistor, the device will have a resistance of 361K at zero degrees C, which is the freezing point of water.  The thermistor is wired into a simple bridge circuit, which uses 1% resistors.  The bridge is connected to a very low power voltage comparator.  The circuit forms a switch circuit, which changes state, when the resistance of the thermistor reaches a certain value.  At zero degrees C the voltage at the non-inverting input of the comparator exceedsCircuit Solution by David A. Johnson P.E.-May, 2006

Freezer Over-Temperature Alarm -  This circuit turns on a beeper whenever the inside temperature of a freezer is greater than zero degrees Centigrade.  The circuit draws only a few microamps from a 9 volt battery.  It uses a glass bead thermistor accurate to 1 degree C.. . . Circuit by David Johnson P.E.-November, 2014

Freezing Temperature Alarm -  The circuit below is designed to activate a beeper alarm, whenever the outside air temperature is below 0 degrees C (32F).    A 9v battery powers the circuit.    The average 9ua current is so low that the battery should last for many years.. . . Circuit by David A. Johnson P.E.-November, 2014

High Temperature Thermocouple activates Relay -  Voltage from a high temperature thermocouple activates a relay when the sensor detects a temperature above 1000 degrees F . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
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Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

12-Bit, 4-20mA Loop-Powered Thermocouple Measurement System using ARM Cortex-M3  -  Required software for the J-Link OB is included in the software installation.  The source code used to test the circuit can be downloaded as a zip file from the ADuCM360 product page.  The source code uses the function libraries provided with the example code.  __ Analog Devices from the Lab

14-Bit, 4-20 mA, Loop Powered, Ther Mocouple Temperature Measurement System using ARM Cortex-M3  -  The duty cycle of the PWM is configured in software to control the voltage across the 47.5 Ω R LOOP resistor, which in turn sets the loop current.__ Analog Devices from the Lab

3-Channel Thermocouple Temperature Measurement System with 0.25 C Accuracy  -  if oil bath measurements are not required, the EVAL-CN0172-SDPZ can be used to measure the three thermocouple temperatures by using the USB interface with a PC and the software provided on the CD.CN0172- UserGuide__ Analog Devices from the Lab

A mV Source for Thermocouple simulation -  I realized early that for prototyping and troubleshooting, I would require a millivolt source which can simulate a type K TC.  For now, this circuit is what I devised.  When the ECU is complete, I will do final calibration with a lab-grade TC simulator, and develop software interpolation of the non-linear curve.    __ 

A precision T/C Amplifier with cold junction compensation for the BS2 -  A thermocouple signal is quite small, and the long thermocouple leads often induce quite a bit of noise into the system.  This new circuit is far more accurate, stable, and less immune to noise.  it makes use of a Linear Technologies LT1025 chip to provide CJC (Cold Junction Compensation) , an LTC1098 8-bit 2-channel Analogue to Digital Converter, and an LTC1050 chopper amp.  The feedback resistors are designed to deliver 5V (full scale signal) to the ADC with a 1000 degree C.  Type K signal.  The 1050 is a great amplifier, delivering "rail to rail" output which makes powering the circuit simple.  __ 

A Simple Circuit Thermocouple Amplifier -  Continuing with the thermocouple interface concept, the next step is to amplify the TC's millivolt signal into a more readable analog voltage, on the order of 0 to 5VDC.  This simple circuit fits the bill.  The LM358N is a dual op-amp IC .  i'm quite sure any op-amp IC would do fine, just be sure it can accept a Vcc which is compatible with your battery pack.  The IC draws ~ 1.0 mA.  __ 

A Thermoelectric Cooler Temperature Controller for Fiber Optic Lasers: Climatic Pampering for Temperamental Lasers -  Linear Technology AN89 __ Designed by Jim Williams - Apr 1st, 2001

Amplifier Thermal Protection -  The thermal protection of amplifiers is always a concern, since overheating is a sure way to reduce the life of semiconductors and other components.    Where you don't want to use a fan (such as in Project 42 - Thermo-Fan for Amplifier Cooling) , then a complete shutdown can be performed.   __ Designed by Rod Elliott  ESP

AN28 - Thermocouple Measurement -  Linear Technology AN28 __ Designed by Jim Williams - Feb 1st, 1988

AN89 - A Thermoelectric Cooler Temperature Controller for Fiber Optic Lasers: Climatic Pampering for Temperamental Lasers -  Linear Technology AN89 __ Designed by Jim Williams - Apr 1st, 2001

Battery-Powered Freezer Alarm -  A typical freezer can contain hundreds of dollars with of food.  if the device becomes unplugged or if the door is left open too long, the food inside can quickly become spoiled.  The hobby circuit below is a battery powered alarm system, which is attached . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Circuit provides Cold-Junction Compensation -  11/28/02  EDN Design Ideas:  The accuracy of any circuit or system that uses a thermocouple to determine the temperature of a process is limited by the accuracy of the method used to perform cold-junction compensation.  in a thermocouple measurement, two wires  __ Circuit Design by Mark Maddox, Analog Devices, Wilmington, MA, and John Wynne, Analog Devices, Limerick, Ireland

Diode Serves as a Sensor for a Thermal Probe -  02/16/12  EDN Design Ideas:  A two-transistor thermal probe can be used to diagnose circuit problems, such as hot components and thermal runaway.   __ Circuit Design by Raju Baddi, Tata Institute of Fundamental Research, Pune, India

DPPs make nonvolatile microvolt DAC -  31-Oct-02 EDN Design Ideas:  The availability of a seemingly limitless variety of monolithic DAC chips makes it easy to implement most digital-to-analog-conversion applications with a single off-the-shelf device.  Sometimes, an unusual set of requirements necessitates a multichip approach, however.  One example of such a requirement is the need for nonvolatility of the DAC's setting in power-up and -down cycles __ Circuit Design by Stephen Woodward, University of North Carolina, Chapel Hill, NC

Freeze Alarm -  I chose an accurate thermistor from Keystone as the temperature sensor for this circuit.  This device has a very specific resistance at a particular temperature.  According to the data sheet for the thermistor, the device will have a resistance of 361K at zero degrees C, which is the freezing point of water.  The thermistor is wired into a simple bridge circuit, which uses 1% resistors.  The bridge is connected to a very low power voltage comparator.  The circuit forms a switch circuit, which changes state, when the resistance of the thermistor reaches a certain value.  At zero degrees C the voltage at the non-inverting input of the comparator exceedsCircuit Solution by David A. Johnson P.E.-May, 2006

Freezer Over-Temperature Alarm -  This circuit turns on a beeper whenever the inside temperature of a freezer is greater than zero degrees Centigrade.  The circuit draws only a few microamps from a 9 volt battery.  it uses a glass bead thermistor accurate to 1 degree C.. . . Circuit by David Johnson P.E.-November, 2014

Freezing Temperature Alarm -  The circuit below is designed to activate a beeper alarm, whenever the outside air temperature is below 0 degrees C (32F).    A 9v battery powers the circuit.    The average 9ua current is so low that the battery should last for many years.. . . Circuit by David A. Johnson P.E.-November, 2014

High Resolution Battery-Powered Robust Type K Thermocouple Signal Conditioning Amplifier with Cold Junction Compensation -  The circuit is used as a plug-in adapter for common digital multimeters and is completely portable.  This circuit employs the LT1025 thermocouple compensator to improve accuracy over a wide range of ambient conditions and is mounted close to the thermocouple connection points for optimal thermal tracking.  it precludes the need __ Linear Technology/Analog Devices App Notes, Apr 8th 2010

High Resolution Type S Thermocouple Digitizer with Improved Cold Junction Compensation -  This simple interface circuit that demonstrates the practicality of direct thermocouple connection to the LTC2400 using low output voltage thermocouples (a Type S thermocouple, as shown, produces a full-scale output voltage of 18mV).  This circuit uses the LT1025, a micropower thermocouple cold junction compensator, to sense __ Linear Technology/Analog Devices App Notes, Apr 8th 2010

High Temperature Thermocouple activates Relay -  Voltage from a high temperature thermocouple activates a relay when the sensor detects a temperature above 1000 degrees F . . . Hobby Circuit designed by David Johnson P.E.-July, 2006

How to Make a Thermocouple Meter with the LTC2492 -  This video explains how to use the 24-bit LTC2492 2-channel delta-sigma analog-to-digital converter with Easy Drive input Current Cancellation to make thermocouple measurements.  The ADCs features and benefits are discussed, as is cold junction compensation; this is followed by a lab demonstration of the LTC2492 thermocouple __ Linear Technology/Analog Devices App Notes, Mark Thoren-Applications Engineering Manager-Mixed Signal Products Sep 15th 2008

Isolated 4-Channel, Thermocouple/RTD Temperature Measurement System with 0.5C Accuracy  -  Turn on the 6 V power supply to power up the evaluation board and SDP board, then plug in the Mini-USB cable into the Mini-USB port on the SDP board.  , Test Launch the evaluation software.  in order for another controller to be used with the EVAL-CN0287-SDPZ evaluation board, software must be developed by a third party.  , CiRCUiT EVALUATiON AND TEST __ Analog Devices from the Lab

LTC2057 Differential Thermocouple Amplifier -  The LTC2057 is a high voltage, low noise, zero-drift operational amplifier that offers precision DC performance over a wide supply range of 4.75V to 36V or 4.75V to 60V for the LTC2057HV.  Offset voltage and 1/f noise are suppressed, allowing this amplifier to achieve a maximum offset voltage of 4μV and a DC to 10Hz input __ Linear Technology/Analog Devices App Notes, Jun 19th 2013

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Thermocouplers:  #'s - N      M - Z

 


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