Process Meter Block PM500

The PM500 is a stand-alone display device that accepts up to two 4–20 mA DC analog input signals.
 The display has four 7-segment LED digits with decimal points.
 The PM500 can be programmed to display any value of user units from ’00.00’ to ‘9999’ and from ‘-0.00 to –
999’.
 The PM500 has either two SPDT relay outputs or four SPDT with programmable functions (UNUSED,
UNDER and OVER).
 The PM500 has an option for 2 16 bit 4 to 20 mA output signals, which are isolated from the 4 to 20 mA input
signals.
 The PM500 display has 5 status LED’s so you can determine which input you are viewing, as well as for
indicating when the PM500 is in the programming, or diagnostics modes. It also signals the user when there is a
sensor failure.
 The PM500 has 2 regulated +24 VDC outputs that can each supply 50 mA maximum. (This supply can be used
to power sensors, etc.).

The LRC feature is a self-check the PM500 performs on its non-volatile memory upon power-up. User variables are stored in the non-volatile memory. If upon a power-up, the new LRC sum matches the previous LRC sum from the non-volatile memory, then the LRC self-check passes. But, if the new LRC sum does not match the previous LRC sum, then the LRC self-check flags an error. An LRC error means the values of at least one variable have been corrupted in the non-volatile memory (i.e., they don’t contain all the user’s previous values).
During an LRC error the PM500 goes into a ‘fail-safe’ mode. It does not show the real-time display, but rather shows the message “LrC”. Also for an LRC error the relay outputs drop-out and the 4-20 mA analog output holds at 4.00 mA due to the corruption of the user variables. To prevent the PM500 from performing abnormally, the PM500 essentially stops performing (because any inadvertent change to the user variables may have changed its performance). The user then obviously knows something is wrong with the PM500’s user variables.