temperature sensing signal for a PT100 or PT1000

They have specialty input cards that accept RTD inputs. You then configure the card for the type of RTD you connected.

You could use a temperature transmitter to convert the RTD to a more common analog signal current or voltage ( 4 to 20ma or 1-5 volts etc). Analog input cards that accept current or voltage inputs are a little cheaper and more flexible.

Cost will vary depending on the manufacture and number of inputs.

I edited my post while curlyandshemp was posting.

Ernie123 said:

How do major PLC manufacturers (Allen Bradley, GE, Siemens, etc.) get the temperature sensing signal for a PT100 or PT1000 into a PLC? Is there additional hardware or software? And what is the cost?

Click to expand...

OR,
you can get RTDs with transmitters built into the heads that transmit that take the PT input and transmit as 4-20ma output.

Advantage of this is the density of a ma Input card versus a PT input card.

For example, Contrologix 1756-IR6 input card only has 6 channels, 1756-IF16 has 16 inputs.

For only 1 or 2 RTDS , best to go with RTD input, but if you have several RTDS, the extra cost of the transmitter in the head is offset by the reduction in 1756 input cards.

What's wrong with MWILSSON?!

Let's research the "temperature sensor" issue first, shall we...?
The are two major types of temperature sensing devices:

1. "dumb" ones, such as ordinary thermocouples (RTDs) which will vary the current running through a bi-metal junction proportionally to the temperature gradient.

2. "smart" ones, which will include the said thermocouple connected to a miniature processor which will determine the current variance and immediately "translate" and scale it into an user available analog/digital signal.

Obviously, if the "sensor" is an RTD, the user will need a dedicated PLC RTD Input Point or PLC RTD Module Point in order to acquire the signal and PLC application programming logic in order process it.

If a "smart" sensor is being used, you might not need any dedicated PLC analog circuitry at all if the sensor provides communications capabilitie; the digital (and already processed temperature data) could be directly routed within the CPU application if the controller posseses the same networking capabilities.

PT 100 is very widely used in process and discrete manufacturing.

PT 1000 is rarely used in process or discrete manufacturing, being mostly an HVAC device.

Consequently, PT100 input cards are available from most, if not all PLC manufacturere (depends on the 'level' of the PLC),

PT1000 inputs are less common, by far.

yes they use added hardware.
for a Pt100 they put a signal of 1 mA into a wire and check the voltage on other wires. 3 or 4 wires

it should be around 100 mV.
Pt1000 needs a 0.1 mA signal. (most of this is two wire system.

dmargineau said:

1. "dumb" ones, such as ordinary thermocouples (RTDs) which will vary the current running through a bi-metal junction proportionally to the temperature gradient.

Click to expand...

Thermocouples are not Resistance Temperature Detectors.

TCs produce a variable voltage signal via a junction of dissimilar metals, while RTDs provide a variable resistance in response to temperature changes.