NTC Thermistor for Temperature Control

mado

Member
M
Join Date
Nov 2011
Location
egypt
Posts
32
I want to measure temperature of room with ntc thermistor and control it with plc.
want some help in choosing the thermistor accurate type.
thanks.
 
any thermistor is good, and a resistor of same value for connected to 10 volts and an analog input is needed.
if no analog input use a 555 (timer IC) and a digital input.
 
if i want high sensitivity what is the best solution RTd or thermistors?.
 
Last edited:
I think you are rapidly getting near the point where you need
1. To study the design characteristics of both RTD and NTC.
2. Talk with mfrs and get their literature. Make sure it includes tolerances

I found in my reading
1. that NTC are not built to a standard like RTD are. Different brands are NOT interchangable as is teh case with RTD
2. RTD has more of a flat line response to temperature than RTC so watch your measurement band and allow for this if needed.

Personally if I want accuracy and good tolerance it is RTD.

Dan Bentler
 
mado said:
ok, now i need to know the suitable shape to be connected to plc.
Click to expand...


Your going to have to explain this again "suitable shape?".

I don't know of any PLC that will accept a thermistor directly, you are going to have to use a transmitter to convert the thermistor to an analog signal to something the PLC can read e.g. 4-20ma, 1-5volts, 0-10 volts.

What PLC do you have and does it have an analog input card?
 
fatek plc has analog input ,I mean with suitable shape something like probe that can be inserted in industrial environment and can be connected to plc via cable.
 
mado said:
fatek plc has analog input
. . .
probe that can be inserted in industrial environment and can be connected to plc via cable.
Click to expand...

Hey Mickey, specific enough?

Put a bigger lure on, we're catching tree-bass so far.
 
mado said:
fatek plc has analog input ,I mean with suitable shape something like probe that can be inserted in industrial environment and can be connected to plc via cable.
Click to expand...

I am not familiar with your PLC, so others will have to comment on that one.

I suppose if your are trying to measure room temperature then any shape will do. As long as it fits thru the door.
 
:)

Is it possible he meant thermocouple? EDIT: No, he has a specific type, either way he will need a transmitter.

To mado:

If you have 24vdc, get an RTD and a suitable transmitter from automationdirect.com

They are cheap, accurate, and I use them in Room Temperature (about 0F to 105F) freezers (-30F to 180F), and gas HVAC heater ducts (30 to 300), and hot water applications (190F).

Very easy to install with the DC Micro connectors:
http://www.automationdirect.com/adc...00)_Sensors/Probes_(with_M12_Cable_Connection)
 
Last edited:
OkiePC said:
:)

Is it possible he meant thermocouple? EDIT: No, he has a specific type, either way he will need a transmitter.

To mado:

If you have 24vdc, get an RTD and a suitable transmitter from automationdirect.com

They are cheap, accurate, and I use them in Room Temperature (about 0F to 105F) freezers (-30F to 180F), and gas HVAC heater ducts (30 to 300), and hot water applications (190F).

Very easy to install with the DC Micro connectors:
http://www.automationdirect.com/adc/Shopping/Catalog/Sensors_-z-_Encoders/Temperature_Sensors_-a-_Thermometers/RTD_(PT100)_Sensors/Probes_(with_M12_Cable_Connection)
Click to expand...
I need thermistor because it's high sensitivity . i need degree of tens like 0.3 which i won't find it in RTD, so i asked your practical experience in this type of measurements . i know many types of sensors available but which one ?. and don't worry about plc i will take care of it.
 
I said i need high resolution ,so thermocouples are rejected and my range is limited no need for thermocouples,beside what is plc problem with thermistors?
 

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