Analog Panel and Switchboard Meters - Introduction

These instruments consist of a moving piece of ferro magnetic material, which is under influence of a current carrying fixed coil. Considering the quadratic nature of the deflecting torque, the scale of these instruments is non-linear. Considering the above mentioned operating process, these instruments are ideally suited for measuring TRMS current and voltage in alternating current circuits. Ammeters are mostly used alongwith externally mounted current transformers, though ammeter upto 100A for direct connection are also provided. Voltmeters upto 750V can be provided. Ammeters with over scale / suppressed scale of 2xIn and 6xIn to withstand high and very high motor starting currents can also be provided. Accuracy for these meters is applicable only within the nominal working range and not in the overscale range.
However please note that all Ammeters can withstand an overload of 10 times the rated range for maximum 5 sec. and 2 times rated currents continuously. When using external current transformer, please ensure that the secondary current value of the CT must be the rated current of the Ammeter i.e., In.

All instruments are designed in accordance with the following international and national regulations : IS-1248; IEC-51; IEC-1010; BS89. The overall dimensions comply with DIN 43700 - 43718.

The operation of these instruments depends on the reaction of the current circulating in a moving coil and the field of a fixed permanent magnet. Considering the operational nature and design of these instruments, the scale is mostly linear.
Since the direction of the movement’s rotation depends on the direction of the current flow (polarity), the moving coil instrument can be used only on direct current circuits. They can be used on alternating current with a suitable rectifier inserted in the circuit. Moving Coil instruments with rectifier for use in alternating current circuits are more sensitive than ferromagnetic or Moving Iron instruments and therefore it is advisable to use them for measuring low value voltage and currents and for applications where low self consumption is required. Moving Coil instruments are generally made for direct input upto 50A. Over 50A, the ammeters are to be used with external Shunts having 60mV or 75mV drop. The Shunts are usually calibrated for a lead resistance of usually less than 0.07 Ohm. When lead resistance is greater than 0.1 Ohm, it is advisable to use shunts of 100, 150 or 300mV drop.

The nominal operating position of the panel meters is vertical. The required mounting position is shown on the scale of the instrument. Instruments with horizontal and angular mounting positions can be supplied on request.

All instruments are designed to withstand 2.5kV RMS, 50Hz, for 1min.

All meter movements are mounted on spring loaded shock absorbing type of jewel bearings which make the instrument
capable of offering good resistance to shocks and vibration. This mechanism is much superior to traditional Taut-Band construction which is highly fragile. The Pivot Jewel mechanism is ideal for aviation, traction and marine applications.

• The ammeters can withstand continuous overloads of 1.2 times the nominal value and short duration overloads of upto 10 times the nominal values for 5 seconds.
• The voltmeters can withstand continuous overloads of 1.2 times the nominal value and short duration overloads of upto 2 times the nominal value for 5 seconds.

• Case: Complies to DIN 43700
• Colour : White
• Front Frame : Complies with DIN 43718
• Colour : Black
• Front Glass : Flat glass on standard models. Anti-glare glass available on request.
• Protection
• Case : IP52; IP54 on request
• Terminals : IP00; IP20(with terminal cover)

• Reference temperature for these instruments is 27ºC ± 20ºC. The standard instruments can operate at a maximum relative humidity of 90%.
• Operating Temperature : -10ºC to + 55ºC, RH<90%
• Storage Temperature : -20ºC to + 70ºC, RH<90%

The pointers are in accordance with DIN 43802.
Instruments scales are n accordance with DIN 43802 regulations. Special scales are available on request.

All the instruments are calibrated according to Accuracy Class specified below as per applicable international standards :

• Moving Iron Meters and Bimetallic Meters are provided with an internal shield cup in order to prevent the influence of stray and low intensity magnetic fields.
• Moving Coil and all other instruments have a center core self-shielding construction which protects against stray and external low intensity magnetic fields.

A screw for zero adjustment is located on the front glass.