Can the HDPQ family of instruments trigger on DC Voltage and Current thresholds?

The answer is YES. Measurement inputs are DC coupled. As long as DC being monitored is within the input channel’s measurement range, the instrument will read the DC as TRMS. The instrument will sample and calculate the TRMS.
XX V DC = XX V RMS

The difference is if you want to set either RMS Thresholds or Transient Thresholds.

If RMS thresholds are set then remember the DC Voltage is RMS Voltage. Nothing special has to be done. Just set the Nominal Voltage on the Nominal & Tracking Page to the DC Voltage. Then know the Voltage RMS Thresholds are calculated and set at +/- 10 % of the Nominal voltage and are listed under the RMS limit button on the Trigger Limit page.

BUT if Transient Thresholds for DC Voltage is desired then you must realize that Transient Threshold are set from the peak value of the Nominal Voltage and manually enter the correct threshold.

The easiest way to explain what has to be done for DC Transient thresholds is by the way of an example:

Let say you are interested in capturing PQ events such as Transient peaks. Special care must be taken with threshold setup. The Transient peak limits are set in terms of Nominal AC Voltage. So if you are measuring 36Vdc for example and enter a Nominal Voltage of 36 Volts, the instrument will assume the nominal peak value is 51 Volts. WHY: because the instrument convert the RMS value to the Peak value when setting transient limits and multiples the Nominal value by the square root of 2. So for a Nominal of 36 V DC, the instrument will assume 36 x 1.41 = 50.76 is the peak of the waveform. You will not be able to set a threshold for Transient peak less than 51v.

To work around this, simply enter a value in the Nominal value screen that will give you the desired Peak value. The only drawback is to be careful about any of the other thresholds. By changing the nominal voltage you will also change the RMS Voltage limits. Remember then the RMS Thresholds will have to be set manually.

Let us continue with the36 V DC example, say we want to set our limits for +/- 10% RMS and a Transient of 42 Volts.

In order to set the transient limit to 42 V we must set the HDPQ nominal voltage such that we can lower the transient limit to 42 V. We need to remember that the Transient limit lowest possible threshold is (1.414) (Nominal Voltage). So for 42 V transient we need to divide 42 V by 1.1414 = 29.7 V

Therefore set the Nominal Voltage to should be set to 29V.

The HDPQ will automatically set the Transient limit to (2.125) X (Nominal Voltage) or 61.625 V Therefore you must manually set the transient limit to 42V

Remember the HDPQ will set the RMS limits to +/- 10% of the Nominal voltage or 31.9V/26.1V, but the RMS limits we want are 39.6V and 32.4V. To get the desired RMS voltages limits, these limits also must be set manually.