Temperature sensor measurement issues behind Honeywell DCS safety barriers

Is it too early? Is there no one? I’ve been waiting for that. I’m working the night shift today

To determine the quality and accuracy of a card, standard instruments must be used. A standard signal is applied at the input terminal of the card, and the signal at its output terminal is measured; only in this way can the quality of the card be accurately assessed...

Just use a signal generator or a standard resistor box to find out

Are points B and C of the card in a short-circuited state just like the resistor, with no voltage present? Should there be voltage?

Are points B and C of the card in a short-circuited state just like the resistor, with no voltage present? Should there be voltage?

I just looked at some posts and recalled that in my previous chemical plant, I used the CS3000 model, which has DC card slots for directly reading the resistance values. I measured and found that points B and C were connected, so I mistakenly assumed that the B and C points of the Honeywell PKS system were also connected. However, this wasn’t the case. In the Honeywell PKS system, the three-wire thermoresistors are fed into the safety gate (I’m not sure if all points go through the safety gate). I checked online and found that after passing through the safety gate, the signal becomes 4-20mA, which is then sent to the DCS. A new question arises: is the voltage measured at the output end of the safety gate? Are points B and C at the input of the safety barrier still conductive? This current-limiting safety barrier with variable resistance seems to change with temperature, haha

For channels with issues, configure them and use a signal generator to test the condition of those channels. After passing through the safety barrier, the temperature signals become 4-20mA signals, in a two-wire system.

So, after passing through the safety barrier, the temperature signals become 4-20mA signals. I see, that’s how it works then

The safety gate has the function of converting temperature signals into current signals. MTL also offers a configurable safety gate, allowing you to change the parameters you need via software – such as the type of thermocouple signal, thermal resistors, measurement range, and more. More and more systems these days do not use temperature cards; instead, they rely on 4-20mA cards, which not only reduces costs but also facilitates the availability of spare parts.

I’m also looking at it; I’m also concerned about this issue