Yokogawa 250 Taut Band and Iron Vane Big Look

New Big Look analog panel meters feature extra-wide scales, big bold numerals above the scale and divisions for unobstructed reading. Tapered needle-sharp pointers and shadow-free acrylic covers help to pinpoint values. Available in taut band and pivot and jewel types. Gasket sealer gives this panel meter a dust and moisture resistant design. (Except 1 1/2").

New Big Look Taut Band - Model 250

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 50G shock. Taut-band meters will withstand 100G shock.

•  New Big Look Taut Band 250 - AC Ammeter
• New Big Look Taut Band 250 - AC Voltmeter
• New Big Look Taut Band 250 - DC Ammeter
• New Big Look Taut Band 250 - DC Voltmeter

Dust Resistant Construction.

YOKOGAWA Big Look panel meters, except 1-1/2”, feature gasketed construction to seal out dust and other air-suspended damaging particles. Application is ideal for adverse environments. Special dust resistant features are included on all YOKOGAWA New Big Look meters (except 1-1/2”). For more severe applications, to meet UL-1437 or IEC 144 requirements, other models are also available upon request.

Clean, Readable Case Design Provides Extra Safety:

YOKOGAWA’s brand New Big Look and Horizon Line panel meters are designed to provide attractive styling, quick, sure readability for any application . . . and a built in safety feature to help you meet national safety requirements. If you must remove the acrylic cover, you have to remove the instrument itself from the panel in order to reach the special safety screws holding on the cover. Removing the meter prevents shock hazard. This safety feature is standard on all New Big Look and Horizon Line meters.

Gasket Sealing Design Establishes A New Industry Standard:

Dust resistant construction is now a standard feature of all New Big Look panel meters 2-1/2” - 4-1/2” only. YOKOGAWA's unique gasket sealing design eliminates the need for a crimped bezel, providing for quick modification and scale changes while maintaining the integrity of the meters.

Taut Band:

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 50G shock. Taut-band meters will withstand 100G shock.

Pivot and Jewel:

In this design the coil and pointer are supported by polished steel pivots at each end which fit into jewel bearings. Pivot and jewel meters 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 meters for applications that involve high shock, but do take advantage of this meter’s ability to withstand vibration.

High-Sensitivity DC Voltmeters:

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.

Expanded-Scale Voltmeters:

For very close monitoring of voltages, Zener diode expanded scale voltmeters are available in 3-1/2- and 4-1/2-inch sizes for AC and DC ratings. Accuracy is ±0.5% of 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.

Frequency Effect - AC Meters:

Iron vane voltmeters are sensitive to frequency and should not be used on frequencies other than design frequency. (Standard voltmeters are calibrated at 60 Hertz. Used at 50 Hertz, accuracy becomes ±2-1/4%. 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:

Rectifier-type meters differ from iron-vane mechanisms in that:
 
They provide a nominally linear (DC) scale rather than conventional iron-vane distribution which has a slight crowding at low end of scale.

• AC current measurements of microamperes and milliamperes at minimum power consumption are permitted.
• AC voltmeters of higher sensitivity (ohms/volt) than iron-vane types can be made.
• Frequency response of rectifier type meters is essentially flat from 20 to 1,000 Hertz (1% effect from reference to 60 Hertz). Rectifier-type meters employ a full-wave rectifier and are available in ratings of 500µA to 30A.
• Suppressed-Zero DC Meters: DC meters can be mechanically suppressed up to 20% of end-scale value. However, additional errors are introduced by suppressions (e.g. errors at 20% suppression = ±3% of end-scale). Many process transmitters in use today provide a 4-20mA signal (occasionally 10-50mA or 1-5mA) and require a suppressed-zero meter with operating zero set. These are known as “live-zero” and are standard.
• Higher Accuracy: Standard calibration accuracy is ±2% of full scale. DC meters can be calibrated to ±1% of full scale as a special model in 3-1/2” and 4-1/2” with mirrored scale.