|
SEARCH
Products
Index
See
List 
Selection
Guide
Applications
Support
Downloads
Reference
Contact
Us
HOME
[Top 
]
|
|
|
Back to
3000 Series
MODELS
(Go
here to ORDER
THESE PRODUCTS) |
 |
Go to
3000 Series
OPTIONS
|
 |
| AC Strain Gage Instruments |
|
|
Models
3178, 3278, 3378 |
|
Being
phase-sensitive carrier-demodulator instruments (rather
than fully DC), these models are
intended for applications involving transformer coupling to the
transducer bridge (as with rotary-transformer torque sensors)
and for applications requiring high sensitivity with optimum
signal-to-noise characteristics—as, for example,
where the electrical environment is especially noisy and there is
a need for high amplification of low signal levels.
The
Model 3178 Strain Gage Conditioner is the basic "Form
1" instrument.
The
Model 3278 Strain Gage Conditioner / Indicator is the "Form
2" instrument, providing vivid front-panel digital
indication of measured values, scalable in desired engineering
units.
The
Model 3370 Strain Gage Conditioner / Indicator / Controller is the "Form
3" instrument, and includes HI/LO limit detection
with control output. |
 |
|
|
|
|
Other
important features include
 |
remote
sensing and regulation of bridge excitation—eliminates errors
from temperature effects on cable resistance |
|
seven-wire
calibration circuitry—applies the internal shunt calibration
resistor at the transducer terminals, thereby eliminating
significant calibration transfer error in long-cable installations |
|
true
differential input, with better than 80 dB of common-mode
rejection—eliminates errors from common-mode pickup and possible
"ground-loop" coupling |
|
input
impedance in excess of 100 megohms preserves the validity of
factory calibration, prevents conversion of common-mode to
normal-mode signals, and eliminates remaining errors attributable to
cable resistance. Allowable cable length has virtually no
practical limits. |
|
elimination
of both short-term and long-term drift through an advanced
solid-state chopper stabilization technique, while preserving the
full frequency passband, free of chopper noise; the rated accuracy
is obtained without "warm-up" period or periodic
"tweaking" of controls |
|
active
low-pass filtering smooths unwanted dynamic signal components
arising from vibration, power impulses, etc., that might prevent
stable digital conversion or control action |
For typical
3278/3378 operations, see the following applications:
3000
Series options applying to these instruments include
| AC
Strain Gage Instrument Specifications [Top
]
(Click
here for 3000 Series General Specifications)
|
|
Input
Type |
Conventional
4-arm strain gage bridge, nominal 90 to 1000 Ω |
|
Input
Range (full-scale) |
Nominal
sensitivity 0.5 to 5 mV/V, full scale* |
|
Excitation
Supplied |
2
VAC (rms) at 3.28 kHz |
|
Analog
Outputs |
Two
outputs, each ±5 VDC full-scale with 50% overrange, 5 mA maximum; low-pass corner
frequencies of 2 Hz and 400 Hz, respectively |
|
Common-Mode
Rejection |
Greater
than 80 dB |
|
Input
Impedance |
Greater
than 100 MΩ |
|
Analog
Filtering |
Active
low-pass filters provide -60 dB per decade above cutoff frequency
("f"); full-scale slew time is 1.4/f sec |
|
Output
Ripple and Noise |
0.15%
of full scale (rms) maximum for 400-Hz output; 0.02% of full
scale (rms) maximum for 2-Hz output |
|
Accuracy
(typical, following calibration) |
0.05%
of full scale |
|
Display
Resolution (Models 3278 and 3378) |
0.02%
of full scale** |
|
*
Ten-turn coarse and fine front-panel controls will balance 1.5 mV/V
initial unbalance and allow span adjustment over the stated full-scale
sensitivity.
** Includes the combined effects of nonlinearity, random noise,
line-voltage variation between 105 and 130 volts, ambient temperature
variation of ±20° F about starting value, and six-months drift of zero
and span. Errors attributable to the transducer are not included. |
|
[Top
]
|
