ANSI C39.1 : 81(R1992)

1. Scope
2. Classification
2.1 General
2.2 Use
2.3 Principle of Operation
2.4 Method of Suspension of Moving Element
2.5 Accuracy Class
3. Definitions
4. Test Conditions
4.1 General
4.2 Reference Conditions
4.3 Mounting
4.4 Number of Readings
4.5 Parallax
4.6 Power Source
4.7 Tapping
4.8 Test Equipment Accuracy
4.9 Thermal Stability
4.10 Preconditioning Time
4.11 Zero Adjustment
5. Test Procedures
5.1 General
5.2 Accuracy, Intrinsic
5.3 Balance, Moving-Element
5.4 Current Loading in Voltmeters (Ohms per Volt)
5.5 Dielectric Test
5.6 Effect of Extreme Temperature
5.7 Effect of Humidity
5.8 Effect of Momentary Overload on Current Circuits
5.9 Effect of Shock
5.10 Effect of Short-Time Overload
5.11 Effect of Sustained Overload on All Circuits
5.12 Effect of Usage
5.13 Effect of Vibration
5.14 Frequency, Dropout Differential (for Synchroscopes)
5.15 Frequency, Pull-in Differential (for Synchroscopes)
5.16 Impedance Test (AC Instruments)
5.17 Influence, Combined Voltage and Current (Wattmeters
      and Varmeters)
5.18 Influence, Circuit-to-Ground Voltage
5.19 Influence, Electrostatic Field on Window
5.20 Influence, External-Magnetic-Field
5.21 Influence, External-Temperature
5.22 Influence, Extreme Temperature
5.23 Influence, Frequency
5.24 Influence, Ferrous-Panel (Panel-Type Instruments
      Only)
5.25 Influence, Ferrous-Platform (Portable Instruments
      Only)
5.26 Influence, Interelement (Polyphase Wattmeters)
5.27 Influence, Operation
5.28 Influence, Position
5.29 Influence, Power-Factor (Wattmeters and Varmeters)
5.30 Influence, Proximity
5.31 Influence, Unbalanced-Current (Polyphase Wattmeters
      and Varmeters)
5.32 Influence, Voltage, at Zero (Wattmeters and Varmeters)
5.33 Influence, Voltage (Frequency Meters and Power-Factor
      Meters)
5.34 Influence, Waveform
5.35 Insulation Test for Leakage Current
5.36 Loading, Apparent Power (Current Circuits)(Volt-
      Ampere Loss)
5.37 Loading, Apparent Power, of Instruments Having
      Voltage Circuits (Volt-Ampere Loss)
5.38 Overshoot
5.39 Repeatability Error
5.40 Resistance (DC Instruments)
5.41 Response Time
5.42 Scale Length
5.43 Sensitivity (Synchroscopes)
5.44 Sticking Above End-Scale Mark
5.45 Sticking Below Low End-Scale Mark (Suppressed-Zero
      Instruments)
5.46 Sticking Below Zero
5.47 Symmetry Error (Offset-Zero Instruments)
5.48 Thermal Converter, 90% Response time
5.49 Tracking Error (Zero-Left and Zero-Right Instruments)
5.50 Tracking Error (Offset-Zero Instruments)
5.51 Voltage Drop (Current-Measuring Instruments)
5.52 Voltage Drop in Current Circuits (Wattmeters,
      Varmeters, and Power-Factor Meters)
5.53 Window Test (When Windows Are a Separate Item
      Assembled to the Cover or Front)
5.54 Zero Adjustment, Range of
5.55 Zero-Shift Error, Short-Term
5.56 Zero-Shift Error, Long-Term
6. General Requirements
6.1 Safety Requirements
6.2 Balancing
6.3 Bearings
6.4 Corrosion Resistance
6.5 Degree of Enclosure
6.6 Finishes
6.7 Hardware for Mounting
6.8 Interior Cleanliness
6.9 Means of Adjustment to Accuracy
6.10 Molded Parts
6.11 Pointers
6.12 Scale Visibility
6.13 Screw Threads
6.14 Terminals
6.15 Windows
6.16 Zero Adjuster
6.17 Dials
6.18 Marking
6.19 Designation of Linear Scales
6.20 Numbering of Scales
6.21 Preferred End-Scale Values for Self-Contained
      Instruments where Zero is at the Left
6.22 Scale Divisions
6.23 Supplemental Data for Portable Instruments - Rated
      Accuracy Class 0.25
6.24 Unit Designation of Quantity Measured
6.25 Bonding
6.26 Ferrous Panels
6.27 Shunt Leads
6.28 Other General Requirements
6.29 Portable-Type Instruments (Introductory Notes and
      General Requirements)
7. Dimensional Characteristics and Detailed Requirements
Table 1 Data to be Furnished with 0.25 Accuracy Class
         Portable Instruments
Figures
1. Positions for Checking Balance Error in Round and
      Rectangular 90-Degree Instruments
2. Positions for Checking Balance Error in Round and
      Rectangular 250-Degree Instruments
3. Positions for Checking Balance Error in Horizontal
      Edgewise Instruments
4. Positions for Checking Balance Error in Vertical
      Edgewise Instruments
5. Linear Scale
6. Dimensions and Drill Plans for Three-Hole Panel-
      Mounted Instruments
7. Dimensions and Drill Plans for Four-Hole Panel-
      Mounted Instruments
8. Dimensions and Drill Plans for Two-Hole Panel-
      Mounted Instruments
9. Dimensions of Edgewise Panel Cutouts
10. Dimensional Characteristics of 6-Inch 90-Degree
      Switchboard-Type Instruments
11. Dimensional Characteristics of 4-1/2 Inch and
      8-3/4 Inch 250 Degree Switchboard-Type Instruments
Appendixes
A. Guide for the User: Panel Cutouts
    Fig.A1. Dimensions of Edgewise Panel Cutouts
    Fig.A2. Dimensions of Cutouts for Back-of-Panel
            Mounted Panel Cutouts, Panel Instruments
B. Minimum Torque Values and Test Procedure for Testing
    Mounting of Terminals
    Fig.B1. Direction and Application of Torque
C. Preferred End-Scale Values for Self-Contained
    Instruments where Zero Is at the Left
    Table C1. End-Scale Values
D. Unit Designation of Quantity Measured
    Table D1. Unit Designations
E. Abbreviations and Unit Symbols Used in this Standard
F. Markings and Symbols for Electrical Indicating
    Instruments
    Table F1. Symbols for Marking Instruments and
              Accessories
G. Terminal Spacing and Size
H. External Resistors and Boxes
    Table H1. Tubular Resistor, Max Current Loading 1mA
    Table H2. Tubular Resistor Dimensions, Inches
I. Enclosures for External Accessories
    Fig.I1. Dimensions of Enclosures

Applies to following including instruments with prefixes such as micro , kilo , etc: ammeters, voltmeters, wattmeters, varmeters (reactive volt ampere meters), frequency and power factor meters, synchroscopes, instruments indicating derived quantities, instruments with self contained electronic devices may apply, to instruments for special requirements, eg, ultrasensitive dc microammeters, high resistance voltmeters, special and unusual ranges, etc. Does not apply to indicating instruments for curve drawing, small instruments eg, small polarized vane ammeters, instruments containing transistors, etc., unless supply obtained from measured quantity, indicating instruments for resistance, conductance or impedance, multifunction instruments or clamp on ammeters