A Pt1000 assembly rating and the Pt1000 element limits serve different purposes. For the SMH2010 case described here, do not replace the type 3 macro limits merely because the assembly is marked -50 to +150 °C. Use the macro's dedicated Alarm output for input-range faults, and protect the physical assembly according to its own marked operating range.
Separate the Assembly Rating from Macro Limits
The -50 to +150 °C marking applies to the complete sensor assembly or housing. The evidence states that operation above +150 °C can damage the housing and operation below -50 °C can cause mechanical failure. These limits therefore constrain installation and process exposure; they do not automatically define the Pt1000 conversion range.
| Value | Meaning supported by the evidence | Engineering decision |
|---|---|---|
| -50 to +150 °C | Marked operating range of the sensor assembly or housing | Keep the installed assembly within this range |
| -60 to +200 °C | Limits present for type 3 Pt1000 in the referenced macro | Do not overwrite them solely to match the housing label |
| -180 to approximately +1700 °C | Claimed span of the Pt1000 sensing element in the supplied evidence | Not established as a certified rating; do not use it to qualify the assembly |
Keep the Type 3 Pt1000 Configuration Intact
The referenced Macro 2.2 identifies Pt1000 as type 3 and contains -60 and +200 °C values. The evidence advises leaving these values unchanged when the only reason for changing them is the assembly's -50 to +150 °C marking. It does not establish whether those macro values are conversion boundaries, diagnostic boundaries, or both, so verify their documented function before editing them.
Leaving the macro unchanged does not authorize operation outside the assembly rating. If the process can cross -50 or +150 °C, apply independent protection based on the assembly limits; do not assume the macro's wider values protect the housing.
Detect Pt1000 Faults with the Alarm Output
That proposed value and delay are not validated fault criteria in the evidence and could represent a legitimate temperature at the assembly boundary.
- Use the temperature macro's Alarm output as the SMH2010 fault indication.
- Configure downstream logic to treat the macro's out-of-working-range condition as a sensor alarm.
- Keep process-limit protection separate from the sensor diagnostic when the assembly's -50 to +150 °C rating is narrower than the configured diagnostic range.
Commission and Verify the Alarm Path
Verify the complete alarm path without exposing the sensor housing beyond its marked limits. Use an approved input-simulation method to create an out-of-range condition, confirm that the macro Alarm output changes state, and verify that the controller or operator interface receives the alarm. Then restore the input and confirm normal operation. The evidence provides no exact recovery timing or reset behavior, so record the observed behavior rather than assuming one.
FAQ
Should I change the Pt1000 macro from -60 to +200 °C to -50 to +150 °C?
No. The evidence identifies -50 to +150 °C as the sensor assembly or housing range and advises against changing the type 3 macro values solely for that reason.
No. Neither -50 °C nor an approximately 3-second delay is established as a disconnection criterion. Use the temperature macro's Alarm output, which indicates an out-of-working-range condition.
How do I detect a Pt1000 fault on an SMH2010?
Monitor the Alarm output from the temperature-sensor macro and route that signal into the required controller or operator alarm logic. Verify it by safely simulating an out-of-range input without taking the physical assembly outside -50 to +150 °C.
