Thermocouple Signal Reading

What type of thermocouple?

At what temperature?

What is the millivoltage being measured?

Look up thermocouple amplifiers.

Yes, read it in millivolt, and divide by 1000.

More seriously, Depending on the type of thermocouple and the temperature difference, I'd expect a few millivolt, and your instrument needs appropriate sensitivity.

Cheers......Codey

You should use voltmeter with millivolt dc range.

We use a microVolt meter which has a high input impedence. Also a Wheatstone bridge works OK

Rok

Yes, I use signal conditioners from Omega Engineering. I amplified the signal and used it in a A to D board in a computer for data aquisition. They work very well.

Thermocouple readinds are in MV. There are digital meters available to measure the temperature for few hundred $. Buy a meter. Amplifying the signal will lead to magnifying the error. There is no problem in data logger for recording readings in MV.
Do not cut your foot to match the shoe.

Absolutelly agree, since thermocouples exhibit a weird curve rather than a proportional mV signal with linearity.

A temperature meter/controller is needed.

Yahlasit

It's not clear whether your thermocouple signal is lower than it should be or if your instrumentation lacks sensitivity. If thermocouple output is too low, try rewelding the junction. If your instrument lacks sensitivity, use an appropriate measuring instrument. Remember that thermocouple extension wires should be the same materials as the thermocouple and that if you are not using an instrument designed for reading your thermocouple materials, you must take mV readings and use a table to compensate for non-linearity.

I am sorry but you are all wrong about losing accuracy using a signal conditioners If speed in measurement is needed use small thermocouple with bare wires. Signal conditioners can cost as low as $50.00 and up depending on the options.

Signal conditioners combine the accuracy of laboratory instrumentation with the performance required by demanding industrial applications. The signal conditioners are ideal for those applications in Data Acquisition, Test & Measurement, Process Control, and Industrial Automation where accuracy, performance, and reliability are critically important. The some signal conditioners mount on a 35mm DIN rail, and operate on any voltage between 10-32 DC power. (A matching 24 Vdc 850 mA switching power supply is also available.) The devices feature three-way isolation of up to 1800 V between the signal inputs, outputs, and power supply.

Other models feature the most widely measured signal inputs: Process (DC) Voltage and Current; Strain Gage; Thermocouples; RTD. s; AC Voltage; AC Current; Frequency/Pulse. The devices are designed to work directly with a variety of sensors and transducers; no other components are necessary. For sensors such as RTD. s, strain gages, and some process transducers, precise stable excitation is provided directly from the module.

Some are available with two different types of signal outputs: Analog or Digital. Providing a totally scalable analog output in DC voltage or current. or provide a digital RS-485 output. Other signal conditioners are intelligent microprocessor based instruments that can be scaled and programmed by computer via serial communications, or over an Ethernet network.

ANALOG OUTPUT
Others feature a 0-10 Vdc, or 0-20 mA (including 4-20 mA) analog output signal that is typically scaled to be directly proportional to the input signal. It is an ideal component in a system with PLC. s or PC. s with analog data acquisition boards.
They are an excellent choice for applications that demand an extra measure of accuracy and performance that is not possible with conventional "analog" signal conditioners or transmitters. Unlike conventional analog devices that are scaled by adjusting zero and span pots, the programmable, micro-processor based instruments are scaled precisely on a PC with free and simple Windows software. Some modules connect directly to a PC. s RS-232 Serial Communications port for programming and scaling. Once the module is configured, the parameters are saved in nonvolatile memory. The device can be disconnected from the PC, or the RS-232 output from the module can be used for continuous data acquisition in addition to the analog output.
Alternatively, the signal conditioner can be connected to a PC. s Ethernet port or an Ethernet network using the EIS-2B module as a Serial/Ethernet bridge.

I agree with the first part of your post.

From whence did you copy the rest? Do you sell this stuff?

No I do not sell signal conditioners, but I sold my patents on detonation flame arresters after using them to pass USCG, CSA, UL, FM, and a number of other standards.

You people can be as condescending as you like but you have not got a glue.Unless you have not actually used them keep your BS to yourself.

I was told that It was impossible. I used K type thermocouples through a signal conditioner and other instrumentation with a fine wire to take 1,250,000. samples per second with an explosion moving 10 time the speed of sound in a pipe line @ 5000 psi in a hydrogen and oxygen mixture.

ref : http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=0&f=S&l=50&TERM1=dwight&FIELD1=&co1=AND&TERM2=brooker&FIELD2=&d=PTXT

Sorry - guess I've come unstuck, there.

"I am sorry but you are all wrong about losing accuracy using a signal conditioners" I don't think anyone has suggested that the use signal conditioners results in loss of accuracy. "If speed in measurement is needed use small thermocouple with bare wires." While it's true that smaller thermocouples will provide faster response to rapidly changing temperature, that's not always a concern. Insulation has little effect on response time and can be very useful for preventing parasitic electrical contacts that can form undesired thermocouple junctions.

Hey..I agree with you that we do not lose accuracy using the signal conditioners. These are commonly used in analog to digital converters. Signal conditioners converts signals so field sensors, transmitters and transducers can interface with indicators, recorders and other PC based systems. These isolate signals to stop erratic measurements caused by group loops using signal conditioners. The process of transferring one signal into another form is known as signal conditioning. Signal conditioning includes amplification, filtering, converting, range matching, isolation and any other processes required to make sensor output suitable for processing after conditioning.

morning ,

hi everyone,thanks for the suggestion.i think i need a detail circuit on how to amplify small signal(ml ) into high voltage 1 to 10 volt.

Knowledge start from basic,but the best knowledge is when u contribute it to mankind

In spite of the personality clashes you find when asking for advice here, almost everyone means well. First, you haven't described your problem in any detail. Second, just adding amplifier gain to a thermocouple is rarely an accurate solution. I suggest you select which thermocouple type to use, then purchase a purpose made signal conditioner to convey the thermocouple signal to your readout device. If your project has unusual requirements such as high temperature, corrosive environment, rapid temperature change, etc., tell us about those conditions. If you are tired of dealing with us, try Omega or Nanmac.com. If you plan to contribute your findings to mankind, make sure they are accurate.

thank you every one, i already solved my problem