Frequently Asked Questions

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General FAQs​

  • What’s the difference between displacement and apparent power factor?

    Displacement power factor is the ratio of the fundamental (60 Hz) real power to apparent power. Apparent power factor is a ratio of total real power (including harmonic component) to apparent power.

  • Can I use the software to assist in verifying a current transformer connection?

    Yes. If no current transformer is connected to a channel that is turned on, then a non-zero reading will be displayed. If the CT is connected but shows a ‘0’ for a value, then the CT is probably connected but the monitored load is turned off. On the other hand if a constant value for current is displayed, a CT wire may have come off of the logger.

  • How can there be a Power Factor of .87 on a 3-Phase Delta lighting load?

    The line currents in a delta are shifted 30° compared to the line-line voltage. One line current will be shifted +30° and the other line current shifted -30° when compared to the line-line voltage. Since power factor is COS(theta), then COS 30° = .866. This will be true for the hardware channels. If the power sum channel (5 or 6) is used, the power factor for the whole load should be as expected.

  • Is the battery on my DENT ELITEpro/DATApro/SMARTlogger rechargeable?

    No. These DENT loggers have single-use Lithium cell batteries that cannot be recharged and should be disposed of properly. Please contact DENT Instruments for replacement batteries.

  • Why am I seeing negative Watts on one phase of a 3-Phase Delta system?

    The line currents in a delta are shifted 30° compared to the line-line voltage. When connected to a load that has a PF of <.5 (>60°) (e.g. a motor not fully loaded) one line current becomes shifted >90° (30° +>60°) when compared to the line-line voltage. The other phase is shifted >30° (-30° + >60°). The COS of an angle >90° is negative, therefore WATTs = COS(theta)VA is negative for that phase. However, as with the power factor the sum of the watts in a delta should be positive. If not, check the CT orientation, one or both may be reversed. Also check to make sure the CT’s are referenced to the correct line voltages.

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Technical Documents

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