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Server script examples

These examples show the usual pattern of a server script: read field signals, decide, and write the result to an internal memory signal. Alarms, screens and the history then use that internal signal like any other: acknowledgement, the alarm list and the event list work without any script code.

Before you begin​

  • You know how to create and save a server script; see Server scripts.
  • The field signals of the examples exist (Motor1.Temperature; Pump1.InletPressure, Pump1.Running), or you replace them with your own.

Steps​

1. Create the internal signals​

In the configuration editor, create internal memory signals of the type on/off: Motor1.TempHigh and Motor1.TempVeryHigh for the first example, Pump1.LowPressureLock for the second. A script may always write to internal memory signals; no command permission is needed.

2. Motor temperature warning​

The script runs whenever the temperature changes, ignores values of bad quality and sets two levels:

defineScript({
  tags: ["Motor1.Temperature"],
  onChange(ctx, path) {
    if (ctx.quality(path) !== "good") {
      ctx.warn("quality not good: " + path + ", skipped");
      return;
    }
    const v = Number(ctx.value(path));
    const veryHigh = v > 85;
    const high = !veryHigh && v > 70;      // high only for 70 < v <= 85
    ctx.setTag("Motor1.TempVeryHigh", veryHigh);
    ctx.setTag("Motor1.TempHigh", high);
    if (veryHigh) ctx.log("Temperature CRITICAL: " + v + " °C");
    else if (high) ctx.log("Temperature HIGH: " + v + " °C");
  },
});

3. Define the alarms​

Define an alarm on Motor1.TempHigh (for example priority high) and on Motor1.TempVeryHigh (priority critical), as for any on/off signal; see Define alarms. The script decides, the alarm engine reports.

4. Pump low-pressure interlock​

The script waits until both inputs have a value and sets the lock while the pump runs with too low inlet pressure:

const PRESSURE = "Pump1.InletPressure";
const RUNNING = "Pump1.Running";

defineScript({
  tags: [PRESSURE, RUNNING],
  onChange(ctx) {
    const p = ctx.value(PRESSURE);
    const run = ctx.value(RUNNING);
    if (p === undefined || p === null || run === undefined || run === null) return;  // both inputs needed
    const lock = Number(run) > 0.5 && Number(p) < 1.5;
    ctx.setTag("Pump1.LowPressureLock", lock);
    if (lock) ctx.warn("Pump running with low inlet pressure: " + p + " bar");
  },
});

Use Pump1.LowPressureLock in an alarm, on the screen, or as a condition for the pump command. If the script should stop the pump itself, it needs Can command field points with a narrow target pattern such as Pump1.Stop; see Writing.

5. Try and activate​

For each script, use Run now / try with the trigger onChange: the result lists the values the script would write, without writing them. Then switch Active on and click Compile and save.

Result​

The internal signals follow the field values; the alarms come and go with them. The Log and status tab of each script shows its log lines and its run and error counts.

Good to know​

  • Keep the decision in the script and the reaction in the alarm definition: the alarm then has its texts, priority, acknowledgement and history without extra code.
  • To load these scripts into several projects at once, save them as .js files and use script import.