Show pump runtime hours with an HMI numeric display

What one count is worth on the numeric display

A numeric display object reads one integer word from the PLC and formats it for the screen. In the object's properties you set the number of decimal places; the panel places the point that many digits in from the right and writes nothing back to the controller. 12345 shown with one decimal place reads 1234.5, and 10 counts read 1.0.

The formatting carries no unit. 1.0 is 1.0 of whatever one count is worth, and the interval that increments the counter sets that worth. Once the HMI driver is configured to the PLC, its tag picker lists the address forms it accepts for the counter's accumulated value; use the form it offers, because an address copied from a different PLC family reads the wrong word or nothing at all.

Choose the unit and the interval first

Decide the unit the operators will read, then set the timer preset to make the digits true:

The table holds only while the timer times the pump-running condition. If the timer runs on the clock instead, the figure measures elapsed time, not pump runtime. This interval-per-count method is also the way to give a PLC hour timer tenths accuracy when a built-in hour counter rounds too coarsely for the maintenance schedule.

Then check the range. Counters in compact PLCs usually hold the accumulated value in a signed 16-bit integer, which tops out at 32,767; a 32-bit counter moves the limit to 2,147,483,647. At 0.1 minute per count, 32,767 counts is 3,276.7 minutes of run time, 54.6 hours. At 0.1 hour per count, the same word holds 3,276.7 hours, about 136 days of run time. Also read the PLC data-file documentation once to learn whether the counter word is retentive; keeping PLC run hours through a power loss covers that setup.

What you need

• A PLC project with one repeating timer and one counter for each pump you track.
• A running feedback signal per pump, a motor starter auxiliary contact or a flow switch, not the start command alone; use the signal that matches the maintenance definition of runtime.
• An HMI panel connected to the PLC through a configured driver, with a screen reserved for the runtime figures.
• The unit and interval picked from the table above.
• A reset policy, written down before the screen goes live: who may zero a total and when.

Build the counting logic

1. Set the timer preset to the interval: 6 seconds for tenths of a minute, 6 minutes for tenths of an hour.
2. Gate the timer with the running feedback so it times only while the pump runs.
3. On the timer-done bit, add one to the counter and restart the timer in the same scan, so one done event produces exactly one count.
4. Decide the partial interval: reset the timer when the pump stops and discard the part interval, or leave it holding so it completes on the next start. Both are correct; the maintenance definition picks one.
5. Restrict counter resets to maintenance. If runtime feeds warranty or regulated records, the PLC total needs controlled reset access and its retention confirmed in the PLC documentation before anyone relies on it.

Bind the numeric display

1. Add a numeric display object to the runtime screen.
2. Address it to the counter's accumulated value using the address form the driver offers.
3. Set decimal places to 1 for the 6-second and 6-minute intervals, and to 0 for whole units. Decimal handling on this object works the same for measured values; showing decimal flow values on an HMI numeric display walks through another case.
4. Write the unit on the label, for example Pump 1 runtime (h). The label and the interval have to agree, because the digits look identical either way.
5. Give each pump its own counter and its own object.
6. If the total also appears on a trend, set that graph's limits for the same implied decimal; setting trend graph limits for implied decimal PLC values covers the scale.

Example: 6-second counts on a pump that runs 4 hours a day

Inputs: the interval is 6 seconds, set in the logic above; the duty is 4 hours a day, the scenario's pump; the counter word is a signed 16-bit integer, full at 32,767 counts, the usual size in compact PLCs.

Rule in words: counts per day equals seconds of run per day divided by the interval in seconds, and days until the word fills equals 32,767 divided by counts per day.

Arithmetic: 4 hours is 4 × 3,600 = 14,400 seconds a day. 14,400 ÷ 6 = 2,400 counts a day, shown as 240.0 with one decimal place. 32,767 ÷ 2,400 = 13.7, so the counter word fills in under 14 days of that duty.

Same pump, 6-minute interval: 4 hours a day is 40 tenths of an hour, so 40 counts a day. 32,767 ÷ 40 = 819 days, about 2.2 years.

Decision: keep 6-second counts when the total is cleared every shift or feeds a shift report; for a meter that has to live between maintenance visits, the 6-minute interval is the choice and the label reads hours.

Check it before you hand it over

• Pump stopped: watch the accumulated value through at least one full interval, 60 seconds on the 6-second choice. No change is expected; a climbing figure points at a timer that is not gated by the running feedback.
• Run the pump for 60 seconds: the counter adds 10 counts and the screen reads 1.0 higher.
• Compare the PLC word with the panel figure digit for digit. PLC right and panel wrong points at addressing or the decimal setting; PLC wrong points at the run feedback, the timer restart, or the counter setup.
• Stop the pump mid-interval and check that the discard-or-hold behavior matches what you decided.
• Power-cycle the PLC once and check the total behaves the way the counter's data type allows.
• Do not release the screen while the unit label is ambiguous, the value moves with the pump stopped, or one interval produces more than one count.

Recommendation: run the counter on a 6-minute interval, show one implied decimal place, and label it in hours for any pump total that has to survive weeks between resets. Keep the 6-second interval for totals cleared every shift and read in tenths of a minute.

Questions