Frequently Asked Questions

Determining Alarm Limits

The RFC-1/B telemetry channel readings can be programmed so that the numbers are spoken more like a human says them. Decimal points and unit words are applied to readings for the benefit of human ears and minds but computers do not work with them easily.

The features that make the RFC-1/B user-friendly can also make it confusing when setting alarms. For instance, humans prefer not to hear leading zeros on numbers but they are significant for the alarm system.

Despite the possible ambiguities, setting the alarm limits is not difficult and need not be complicated. There is a simple method to determining appropriate alarm limits for a telemetry channel.

Telemetry Channel Reading

Alarm limits are based entirely on the reading of the channel that is being monitored. Before programming an alarm, the channel must be programmed and the typical input voltage should be applied. If the RFC-1/B is already installed then this has probably been done.

To determine the alarm limits, you just need to look at the channel reading the way the RFC-1/B does.

  • Readings always have four significant digits
  • Decimal points are ignored
  • Unit words do not exist

Take a reading on the channel–write it down if you need to. If you hear a decimal ignore it. If you do not hear four digits, add zeros to the left until the number has four digits. This is the channel reading as the RFC-1/B sees it.

Internal Channel Reading Generator

This tool can show you what a channel reading looks like as it is stored in the RFC-1/B. Enter the numeric portion of the channel reading exactly as the RFC-1/B says it.

Enter a channel reading:

The internal reading is:

Setting alarm limits is easy once you have the correct channel reading as a reference. Suppose a channel reads 98.7% and you want limits at 105% and 90%. The internal reading is 0987. Using this as the reference value, upper and lower limits would be 1050 and 0900 respectively.