What Range High and Range Low Control
In DTCOM, Range Low and Range High define the lower and upper measurement scale for the process value (PV). They also establish the boundaries within which the set value (SV) can be entered. The settings therefore affect both PV scaling and the permitted SV range; they are not confirmed as protective shutdown thresholds.
For an analog sensor type such as 0–10 VDC or 4–20 mA, assign Range Low and Range High to the engineering values represented by the signal endpoints. The evidence does not provide engineering units or required endpoint values, so derive them from the connected sensor specification.
Separate Scaling Limits from a High-Limit Trip
| Function | Supported interpretation | Safety implication |
|---|---|---|
| Range Low | Lower boundary of the sensor measurement scale and SV entry range | Do not assume it acts as a low-limit shutdown |
| Range High | Upper boundary of the sensor measurement scale and SV entry range | Do not assume it switches the controller off when PV exceeds the value |
| High-limit protection | No shutdown function or behavior is identified in the evidence | Verify a separate alarm, interlock, or protective device |
Configure a Safe High-Limit Response
Because the available information only confirms scaling and SV restrictions, treat automatic shutdown as an unverified function. Do not use Range High alone as the protective trip until the controller documentation and a functional test confirm that behavior.
- Configure the sensor type, then assign Range Low and Range High from the sensor’s specified measurement span.
- Choose the required high-limit trip from the process risk assessment; do not substitute the top of the sensor scale automatically.
- Identify and configure a dedicated alarm or cutoff function if the controller provides one. If it does not, use an independent high-limit interlock that removes energy from the final control element.
- Define the required reset behavior so the process cannot restart unexpectedly after the PV falls below the limit.
Verify the Protection Before Operation
Perform a controlled test that raises or simulates PV across the selected trip point. Confirm the displayed PV follows the configured scale, SV cannot be entered outside the intended range, and the separate high-limit function de-energizes the controlled output as designed. Also test reset, controller power cycling, and sensor-fault behavior; the evidence does not define how the controller handles these conditions.
FAQ
Does DTCOM Range High turn the controller off?
The evidence identifies Range High as the upper sensor scale and SV boundary, not as a confirmed shutdown threshold. Use and test a dedicated alarm or high-limit interlock for shutdown.
Do Range High and Range Low limit PV or SV?
They define the PV measurement scale and consequently the lower and upper values available for SV entry.
How should I scale a 0–10 VDC or 4–20 mA sensor in DTCOM?
Set Range Low and Range High to the engineering values represented by the sensor’s signal endpoints. Obtain those values and units from the sensor specification.