iv
Suspension
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 mecha-
nisms. The absence of friction
resulting from this pe rmits greater sensi tivitie s
and provide s more rugged meters.Common
failures of conve ntional mete rs subjected to
shock testing are cracke d jewels and/or
blunte d pivots. Taut band, without pivot and
jewels, conseque ntly, will withstand shock in
exce ss 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 bea rings. Pivot and
jewel mete rs 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 go od performance
from the pivot and jewel construction is the
reason fo r its long popularity. Don’t specify
pivot and jewel meters fo r applications that
involve high shock, but do take advantage
of this mete r’s ability to withstand vibration.
High-se nsitivi ty DC Voltmeters
Standard DC voltmeter se nsitivi ty is 1000
ohms/volt. Expresse d dif ferently, 1000
ohms/volt sensitivi ty means that the meter
draws approximately one milliamp full-scale
current.
Occasionally lower cur rent drains are
necessar y, hence higher sensitiv ities may be
required. The table below compares available
sensitiv ities, maximum self-containe d
voltages, and approximate full-scale currents.
The voltage range could be extende d by
using exter nal resisto rs.
Expanded-s cale Voltmeters
For very close monitoring of voltages, Zener
diode expanded scale voltmete rs are
available in 31⁄2- and 41⁄2-inch sizes fo r 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 f rom 12
to 300 volts. Minimum span is 16% of
mid-span value.
Frequency Ef fect — AC Meters
Iron vane voltmete rs are sensitive to
freque ncy and should not be used on
freque ncies other than design frequency.
(Standard voltmeters a re calibrated at 60
Her tz. Used at 50 He r tz, accuracy becomes
±21⁄4%. There are also 150- and 300-volt
ratings listed which are calibrate d at 400
Her tz). For calibrations at freque ncies other
than 60 and 400 Hertz, refer to facto r y.
All Iron-vane ammeters (which produce a
conventional scale distribution with divisions
crowde d in lowe r third of scale) from 10
milliamperes to 50 amperes are virtually unaf-
fecte d by a change in frequency; e.g., a stock
ammeter (calibrate d at 60 Her tz) when used at
400 Her tz incurs an additional error of only .5
percent full-scale. If use d on 1000 Her tz, the
additional error is 4 percent. We recommend
use of stock (60 Her tz) ammeters on any
freque ncy in the range of 25 Hertz to 400
Her tz. For calibration at freque ncies outside
the 25-Hertz to 400-Her tz range, refe r to
factory o r use a rectifier-type AC ammeter.
Rect ifie r-t ype Meters
Rectifie r-type meters differ from iron-vane
mechanisms in that:
•They prov ide a nominally linea r (DC) scale
rather than conventional iron-vane distribution
which has a slight crowding at low end of
scale.
•AC cur rent measurements of microamperes
and milliamperes at minimum power
consumption are permit ted.
•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%
ef fect from refe rence to 60 Hertz).
Rectifie r-type meters employ a full-wave
rectifier and are available in ratings of
500µA to 30A.
Suppressed-ze ro DC Meters
DC meters can be mechanically suppressed
up to 20% of end-scale value. Howeve r,
additional errors are intro duced by sup-
pressions; e.g.,
Errors at 20% suppression = ±3%
of end-scale
Many process transmitters in use today
provide a 4 -20mA signal (occasionally 10 -50
mA 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 calibrate d to ±1% of
full scale as a special model in 31⁄2” and 41⁄2”
with mirrored scale.
Conduit Mount ing Case — 21⁄2-inch New Big
Look Meter
Available only for 21⁄2-inch Type 250 panel
meters, for indoor or outdoor use, the conduit-
mounte d case provides prote ction to the meter
under severe environmental conditions. The
conduit case is both sealed and weatherproof
and is pre-drilled, ready fo r mounting of sepa-
rately ordered panel meters. Assembly of meter
into case is done by purchaser. (Drawing No.
2579K10700.)
Data s ubject to change w i thou t not ice.
SERIES ST YLIST BIG LOOK & HORIZON LINE
SIZE/RATING 11⁄221⁄231⁄241⁄211⁄221⁄231⁄241⁄2
DC CURRENT 10µ A 20µ A 50µ A
DC VOLTAGE 50mV 50mV
AC CURRENT (IRON VANE) --- 10mA --- 10mA
AC VOLTAGE (IRON VA NE) --- 3V --- 3V
AC CURRENT (RECTIFIER) 1mA 500µ A
AC VOLTAGE (RECTIFIER) 3V 10V
DC CURRENT 10A 50A 15A 30A 50A
DC VOLTAGE 1000V 300V 600V
AC CURRENT (IRON VANE) --- 50A --- 30A 80A
AC VOLTAGE (IRON VANE) --- 600V --- 300V 600V
AC CURRENT (RECTIFIER) 100mA 30A 20mA
AC VOLTAGE (RECTIFIER) 600V 150V 300V
New Big Look, Horizon Line and Stylist
Pan el Meters
Maximum and Minimum Ratings
In general, the maximum and minimum
ratings of current and voltage are those
listed in “Ratings.” Listed a re rating limits
for self-contained meters.
Ratings greate r than those listed can be
accomplished by use of exte rnal shunts,
resistors or transfo rme rs. Meters to be
used with external accessor ies a re shown
in “Ratings.” See page 29 fo r Shunts,
resistors and Transformers.
MINIMUM RATING
MAXIMUM RATING