255-250-DNDN-UL YOKOGAWA, 255-250-DNDN-UL Datasheet - Page 5

• Manufacturer Part Number: 255-250-DNDN-UL
• Description: FREQUENCY PANEL METER MODEL 255-2 55-65HZ 240VAC UL
• Manufacturer: YOKOGAWA

Specifications of 255-250-DNDN-UL

• Meter Range: 55Hz To 65Hz
• Meter Size/dimensions: 2.5" X 2.5"
• Scale Length: 2.06"
• Meter Function: Frequency

iv
New Big Look, Horizon Line and Stylist
Panel Meters
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
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.
Maximum and Minimum Ratings
In general, the maximum and minimum
ratings of current and voltage are those
listed in “Ratings.” Listed are rating limits
for self-contained meters.
Ratings greater than those listed can be
accomplished by use of external shunts,
resistors or transformers. Meters to be
used with external accessories are shown
in “Ratings.” See page 29 for Shunts,
and resistors.
SERIES
SIZE/RATING
DC CURRENT
DC VOLTAGE
AC CURRENT (IRON VANE)
AC VOLTAGE (IRON VANE)
AC CURRENT (RECTIFIER)
AC VOLTAGE (RECTIFIER)
DC CURRENT
DC VOLTAGE
AC CURRENT (IRON VANE)
AC VOLTAGE (IRON VANE)
AC CURRENT (RECTIFIER)
AC VOLTAGE (RECTIFIER)
Expanded-scale Voltmeters
For very close monitoring of voltages, Zener
diode expanded scale voltmeters are
available in 3
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
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:
•
rather than conventional iron-vane distribution
which has a slight crowding at low end of
scale.
1
⁄
4
They provide a nominally linear (DC) scale
%. There are also 150- and 300-volt
1
⁄
2
- and 4
1
⁄
2
-inch sizes for AC and
100mA
10A
---
---
1
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1
⁄
2
2
MAXIMUM RATING
MINIMUM RATING
STYLIST
1
⁄
2
1000V
50mV
10mA
10µA
600V
600V
1mA
50A
50A
30A
3
3V
3V
1
⁄
2
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 sup-
pressions; e.g.,
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 calibrated to ±1% of
full scale as a special model in 3
with mirrored scale.
Conduit Mounting Case — 2
Look Meter
Available only for 2
meters, for indoor or outdoor use, the conduit-
mounted case provides protection to the meter
under severe environmental conditions. The
conduit case is both sealed and weatherproof
and is pre-drilled, ready for mounting of
separately ordered panel meters. Assembly of
meter into case is done by purchaser. (Drawing
No. 2579K10700.)
Data subject to change without notice.
•
and milliamperes at minimum power
consumption are permitted.
•
(ohms/volt) than iron-vane types can be
made.
•
is essentially flat from 20 to 1,000 Hertz (1%
effect from reference to 60 Hertz).
Errors at 20% suppression = ±3%
AC current measurements of microamperes
AC voltmeters of higher sensitivity
Frequency response of rectifier type meters
4
of end-scale
1
⁄
2
15A
1
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1
BIG LOOK & HORIZON LINE
⁄
2
300V
150V
1
⁄
2
-inch Type 250 panel
20µA
300V
30A
30A
2
1
⁄
2
500µA
50mV
10mA
20mA
10V
3V
1
⁄
2
-inch New Big
1
3
⁄
2
1
" and 4
⁄
2
600V
600V
300V
50A
80A
50µA
1
⁄
4
2
"
1
⁄
2