PT100 difference on 1746-NR4 Card ?

504bloke

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Hi

Just programming and configuring an 1746-NR4 card for an SLC system

on the Configure box drop down menu for Types of Input

I have 2 sorts of Pt100

ie

100 Pt 385 and 100 Pt 3916

Whats the difference ?

My customer has told me that this input needs to be Pt 100 3 wire, i have no other information...
 
100 Pt 385 and 100 Pt 3916 types refer to the resistance change vs temperature change curve. The 385 is the most common. IIRC, an RTD reads the ohms it's rated at freezing (0 C., 32 F.).
 
385 is standard DIn and is widely used.
391 is JIS japan standard and is used by japanese companies.
difference is simple on 100 celsius DIN will be 138.5 ohms and the JIS will be 139.1 ohms. So use a simple ohmmeter in boiling water and presto.
on zero you will not see any difference.

if mounting 3 wire only 3 wires should be connected and when a 4 wire is present just do not connect it anywhere.
greetings polleke
 
shooter said:
... So use a simple ohmmeter in boiling water and presto.
on zero you will not see any difference....

You could tell the difference if you have both types by doing this, however the temperature of water boiling at 100C (212F) is only when at one standard atmosphere. Depending on the weather and your local elevation (barometric pressure), it could be higher or lower.
 
You guys are close, but not quite nailing it.

The two numbers represent the Thermal Coefficient of Resistance, Ohms/Ohm/°C, which is the amount the resistance of the RTD changes as the temperature of the RTD changes. The European coeeficient, 0.00385 Ohms/Ohm/°C is the most common, and if you have no contrary information is probably the correct value. The other coefficient, 0.00392 Ohms/Ohm/°C is the "American" curve, but it is not often encountered in either the US or Europe.

Both types of RTDs have a resistance of 100 Ohms at 0 °C. At 100 °C the common European curve RTD will have a resistance of 138.51 Ohms, and the other curve will have a resistance at 100 °C of 139.16 Ohms.

These two points allow crude calibration checks, since ice water is approximately 0°C and boiling water is approximately 100°C. There is variation with elevation and salinity and so on but for a quick check these values are close enough.
 
Last edited:
Hello to all, I am about to purchase a RTD thermometer but I am very confused as to the type of RTD sensors. I am looking at an Amprobe RTD-10 and the description says PT3916/PT3926/PT385 standard. From the basic instrumentation training that I took years ago, I know that there is a PT100 and a PT1000, both physical RTD devices. I tried searching for either a PT385, 3916, and 3926 but couldn't find a physical device, only tables that refer to each one of them as being European, American, and Japanese calibrations. After doing more research, am I correct in thinking that what I need to use would be a PT100 sensor and then actually heat them up and measure the resistance values. And after that I will compare the values to the tables and then configure the meter accordingly? Will someone be able to enlighten me on this?
 

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