---

Application Information

New Big Look, Horizon Line and Stylist Panel Meters

Taut band is a means of suspending the moving mechanism between two ribbons of metal, obviating the need for pivots, jewels and control springs found in conventional mechanisms. The absence of friction resulting from this permits greater sensitivities and provides more rugged meters. Common failures of conventional meters subjected to shock testing are cracked jewels and/or blunted pivots. Taut band, without pivot and jewels, consequently, will withstand shock in excess of that specified for pivot and jewel meters. For example, ANSI Specifications for panel meters require 5OG shock. Taut-band meters will withstand 100G shock.

In this design the coil and pointer are supported by polished steel pivots at each end which fit into jewel bearings. Pivot and jewel instruments are recommended for high vibration environments because of the mechanism's inherent stability and strength. Accuracy and repeatability are almost equal to the taut-band's, and good performance from the pivot and jewel construction is the reason for its long popularity Don't specify pivot and jewel instruments for applications that involve high shock, but do take advantage of this instrument's ability to withstand vibration.

Standard DC voltmeter sensitivity is 1000 ohms/volt. Expressed differently, 1000 ohms/volt sensitivity means that the meter draws approximately one milliamp full-scale current.

Occasionally lower current drains are necessary, hence higher sensitivities may be required. The table below compares available sensitivities, maximum self-contained voltages, and approximate full-scale currents. The voltage range could be extended by using external resistors.

For very close monitoring of voltages zener diode expanded scale voltmeters are available in 31/2- and 41/2-inch sizes for AC and DC ratings. Accuracy is ±0.5of full-scale value. Standard voltage spans are listed in "Ratings."

Expanded scale voltmeters can be Furnished for any mid-span values from 12 to 300 volts. Minimum span is 16% of mid-span value.

Iron vane voltmeters are sensitive to frequency and should not be used on frequencies other than design frequency. (Standard voltmeters are calibr ated 60 Hertz. Used at 50 Hertz, accuracy becomes ±21/4 %. There are also 150. and 300-volt ratings listed which are calibrated at 400 Hertz). For calibrations at frequencies other than 60 and 400 Hertz, refer to factory.

All iron-vane ammeters (which produce a conventional scale distribution with divisions crowded in lower third of scale) from 10 milliamperes to 50 amperes are virtually unaffected by a change in frequency; e.g., a stock ammeter (calibrated at 60 Hertz) when used at 400 Hertz incurs an additional error of only .5 percent full-scale. If used on 1000 Hertz, the additional error is 4 percent. We recommend use of stock (60 Hertz) ammeters on any frequency in the range of 25 Hertz to 400 Hertz. For calibration at frequencies outside the 25-Hertz to 400-Hertz range, refer to factory or use a rectifier-type AC ammeter.

Rectifier-type meters differ from iron-vane mechanisms in that: