NOTE In the following tests, polyphase meters shall be tested on a single-phase circuit, with the current windings in series and the voltage windings in parallel.

Test No. 1 Accuracy of Registration

27 The indication of an acceptable meter after having normal voltage and twenty-five percent (25%) rated current applied for at least one (1) hour shall not differ from the true value at twenty-five, fifty, and one hundred percent (25, 50 and 100%) of full-scale reading by an amount greater than two percent (2%) of full-scale indication. The test shall be made first ascending the scale from twenty-five percent (25%) to one hundred percent (100%), and next descending the scale from one hundred percent (100%) to twenty-five percent (25%) of fullscale indication. The corresponding readings shall not be averaged, but the maximum error shall in each case be the only one considered.

The tests shall be made at calibration voltage, rated frequency and at unity power factor.

Test No. 2 Equality of Elements Three-wire and Polyphase Meters

28 The current required to give an indication of one-half (1/2) full-scale indication when passed through either current winding alone shall not differ by more than two percent (2%) from twice the current required to give the same indication with the current windings in series.

Test No. 3 Effect of Variation in Voltage

29 The indications of an acceptable meter when subjected to a voltage differing from the calibration voltage by plus or minus ten percent (10%) of the calibration voltage, shall not vary from the indications at corresponding loads and calibration voltage by more than one and one-half percent (1.5%) of fullscale indication. Tests shall be made at approximately fifty and one hundred percent (50 and 100%) of full-scale indication, at, rated frequency and unity power factor.

Test No. 4 Effect of Variation in Power Factor-Single-Phase and Polyphase Meters

30 The indications of an acceptable meter under the test conditions shall not differ from the indications at corresponding

loads and unity power factor by an amount greater than two percent (2%) of the full-scale deflection.

The tests shall be made at calibrated voltage and at rated frequency.

Each meter shall be tested at the various values of current and lagging power factor given below:

Test No. 5 Effect of Variation in Frequency-Single-Phase and Polyphase Meters

31 The indications of an acceptable meter tested at ninetyfive percent (95%) and one hundred and five percent (105%) of rated frequency shall not differ from the corresponding indications at rated frequency and corresponding load by an amount greater than one and one-half per cent (1.5%) of full-scale indication.

Tests shall be made at approximately fifty and one hundred percent (50 and 100%) of full-scale deflection.

Test No. 6 Effect of Variation in Temperature

32 This test shall be made as prescribed in Section IV, paragraph 42, of the Meter Code, except that the test shall be made at fifty percent (50%) and one hundred percent (100%) of rated current. The temperature co-efficient of an acceptable meter as so determined shall not exceed one-quarter percent (0.25%) per degree centigrade.

Test No. 7 Damping

33 The tests shall be made at calibration voltage, rated frequency and at unity power factor.

In an acceptable meter, a sudden increase in the load from fifty percent (50%) of rated current to seventy-five percent (75%) of rated current shall not cause the pen to overtravel by more than ten percent (10%) of full-scale indication, and the pen shall come to within three percent (3%) of its final deflection in a time interval not greater than fifteen (15) seconds. Test No. 8 Sensitivity

34 With a steady current supply at the calibration voltage,

rated frequency and at unity power factor, the sensitivity shall be such that the pen responds immediately to a change of current equal to two percent (2%) of the current corresponding to full-scale deflection of the instrument. The test shall be made at approximately three-quarters (3/4) of full-scale deflection. Test No. 9 Timing

35 The chart shall be set to indicate true time and two (2) records of twenty-four (24) hours each shall be taken, one (1) with the pen at the full-scale position, and one (1) with the pen at one-quarter scale position. The time indicated on the chart shall not exceed plus or minus one-quarter percent (0.25%) of the elapsed time. The chart shall be reset to indicate correctly the beginning of the second twenty-four (24) hour test. Test No. 10 Legibility of Record

36 The deflection of the pen shall be such that at any point on the scale from one-quarter scale to full scale, the record may be read to within one percent (1%) of the full-scale indication. The travel of the pen from the no-current position to the fullscale position shall not be less than two and one-half (2.5) inches.

Class II Integrated Demand Meters

Test No. 1 Acceptability of Integrating Meter

37 The integrating meter which constitutes the measuring portion of integrated-demand meters shall be subjected to the tests for acceptance for meters of its class in Section IV. All auxiliary devices necessary for the measurement of demand shall be in train and in full operation during these tests. The limits. of allowable variations for an acceptable meter shall be the same as fixed in Section IV for corresponding meters unconnected to registering or recording devices.

Test No. 2 Steps per Demand Interval

38 The number of steps or their equivalent per demand interval at the rated load of the integrating meter shall be sufficiently great so that in no case the error introduced thereby shall exceed two percent (2%).

Test No. 3 Legibility of Record-Indicating and Graphic Recording Devices

39 The indication or record shall be such that at any point between one-quarter full scale and full scale it can be read to within one percent (1%) of the full-scale value.

Test No. 4 Equality of Energy Intervals

40 The integrating meter shall be operated on a constant load of approximately one hundred percent (100%) of its rated capacity during the time necessary for five (5) complete revolutions of the contact wheel which sends energy impulses to the recording or registering device. The times shall be recorded at which each such energy impulse is transmitted, and by subtraction, the time intervals between the energy impulses shall be found. In an acceptable device, no such energy interval shall differ from the mean of all the energy intervals by more than one percent (1%) of the time of one (1) complete revolution. Test No. 5 Accuracy of Demand Intervals

41 The duration of the demand interval shall be measured throughout three (3) entire cycles of the operation of the timing mechanism. The length of such interval shall not differ from the nominal length by more than thirty-six (36) seconds. Test No. 6 Accuracy of Contact Mechanism

The integrated-demand meter consisting of an integrating meter with contact mechanism and of the corresponding registering or recording mechanism shall be operated on a load approximately equal to the full load of the integrating meter during a period of time such that not less than five hundred (500) energy impulses are transmitted. A record of these impulses shall be taken on a suitable graphic instrument (e. g., an adapted laboratory chronograph) an inspection of the chart of which will show whether the contact mechanism has failed either by sending out double impulses or by omitting any impulse. In an acceptable type of contact mechanism no such failure shall occur. Test No. 7 Accuracy of Registering or Recording Mechanism

43 Using the data of Test No. 6, the total number of energy impulses shown by the registering or recording mechanism shall be compared with the total number as given on the chart of the graphic instrument. In an acceptable type of registering or recording mechanism, these numbers shall be equal. In the case of recorders or indicators which reset, it is evident that the impulses lost during the reset period are not to be considered.

NOTE In tests Nos. 6 and 7, the graphic instrument used shall have such electrical constants and shall be connected in the circuit in such a way that it will not interfere with the reliability of operation of either the contact mechanism or the registering on recording mechanism.

Test No. 8 Clock

44 Two (2) twenty-four (24) hour tests shall be made. one near the beginning and the other near the end of the winding period. In an acceptable meter the gain or loss of the clock in either test shall not exceed two (2) minutes in twenty-four (24) hours.

Test No. 9 Timing Motors

45 In meters using an electric motor instead of a clock, the timing motors shall be tested as follows:

(a) At calibration voltage and at rated frequency, the average rate of the motor during a demand interval shall be such as to correspond to a gain or loss of time not to exceed two percent (2%).

(b) Effect of Voltage Variation on Timing Motor A variation of five percent (5%) above or below the rated voltage of the timing motor shall not affect the speed of the motor by more than one percent (1%).

(c) Effect of Frequency Variation A variation of three percent (3%) above or below the rated frequency of the current applied to the timing motor shall not affect the speed of the motor by more than six percent (6%).

(d) A rise in temperature of ten degrees (10 deg.) centigrade above an initial temperature of twenty degrees (20 deg.) centigrade shall not change the speed of the motor by more than two percent (2%).

Class III Time-Lagged Demand Meters

NOTE Polyphase meters shall be tested on a single-phase circuit, with their current windings in series and their voltage windings in parallel.

Test No. 1 Accuracy of Indication

46 (a) Meters in which the speed of the indicator is proportional to the load.

Each meter shall be tested on a load corresponding to twentyfive, fifty and one hundred percent (25, 50 and 100%) of fullscale indication, at calibration voltage, rated frequency and at unity power factor as follows:

With the indicator at the no-load position, a load of the prescribed amount shall be suddenly thrown on. The indication shall be noted when one-half (1/2) of the rated demand interval