Measurement Computing 142 User manual

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 1 of 11 t&[email protected]m
TM
Model 142 Inline Strain Gage Amplifier
Measurement Specialties, Inc.
Vibration Sensors Design Center
32 Journey, Suite 150
Aliso Viejo, CA 92656 USA
Tel: [phone]
www.meas-spec.com
[e-mail]

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 2 of 11 t&[email protected]m
TM
Warranty
Measurement Specialties, Inc. accelerometers
are warranted during a period of one year from
date of shipment to original purchaser to be free
from defects in material and workmanship. The
liability of Seller under this warranty is limited to
replacing or repairing any instrument or
component thereof which is returned by Buyer,
at his expense, during such period and which
has not been subjected to misuse, neglect,
improper installation, repair, alteration, or
accident. Seller shall have the right to final
determination as to the existence and cause of a
defect. In no event shall Seller be liable for
collateral or consequential damages. This
warrant is in lieu of any other warranty,
expressed, implied, or statutory; and no
agreement extending or modifying it will be
binding upon Seller unless in writing and signed
by a duly authorized officer.
Receiving Inspection
Every Measurement Specialties, Inc.
accelerometer is carefully inspected and is in
perfect working condition at the time of
shipment. Each accelerometer should be
checked as soon as it is received. If the unit is
damaged in any way, or fails to operate, a claim
should immediately be filed with the
transportation company.
Service Concerns
If a Measurement Specialties, Inc. instrument
requires service, first contact the nearest
Measurement Specialties, Inc. representative.
They may be able to solve the problem without
returning the unit to the factory. If it is
determined that factory service is required, call
Customer Service at the regional headquarters
for an RMA number before return.
Returns
All units being returned to the factory require an
RMA (Return Material Authorization) number
before they will be accepted. This number may
be obtained by calling Customer Service at the
regional headquarters with the following
information; model number(s), quantity, serial
number(s), and symptoms of the problem, if
being returned for service. You must include the
original purchase order number if under
warranty.
Recalibration Services
The Vibration Sensors Design Center and its
two manufacturing facilities in China and France
offer factory re-calibration services for Variable
Capacitance, Piezoresistive, Piezoelectric
(including IEPE, ICP etc.) accelerometers and
Electronics. NIST (US), DKD (Germany),
COFRAC (France) traceable calibration services
on sensitivity at 100 Hz (102 or 120 Hz in
Europe) and full frequency sweeps are offered.
Contact the regional headquarters for pricing
information.
Inquiries
Address all inquiries on operation or applications
to your nearest Sales Representative, or to the
Vibration Applications Support as follows:
Global Headquarters
1000 Lucas Way
Hampton, VA 23666, USA
Tel: [phone]
Vibration Sensors Design Center
32 Journey, Suite 150
Aliso Viejo, CA 92656, USA
Tel: [phone]
European Headquarters
Impasse Jeanne BENOZZI
CS 83 163, 31027 Toulouse Cedex 3, France
Tel: [phone]
Asian Headquarters
Measurement Specialties (China), Ltd.
No. 26 Langshan Road
Shenzhen High-Tech Park (North)
Nanshan District, Shenzhen 518057, China
Tel: [phone]

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 3 of 11 t&[email protected]m
TM
Description
The Model 142 is a remote in-line strain gage amplifier designed to be used with ¼ bridge strain
gage instruments (half bridge option, see page 9). The amplifier features five user selectable
gain settings with a gain accuracy of ±0.5% and offers a wide bandwidth to 100kHz. The model
142 offers a patent pending Auto-Zero function that allows the operator to zero the transducer
offset voltage to within ±1.5mV.
Specifications
Dynamic
Input Type
Uniaxial Strain Gage, 4 Wires, ¼ Bridge
Input Range (V)
0.5 to (Vexc –0.6), each input referenced to ground
User Selectable Gain Settings
x10, x50, x100, x200, x500
Bandwidth (-3dB)
DC to 100kHz
Noise (nV/√Hz)
30 RTI + 2000 RTO
Zero Output After Auto-Zero Actuation1
±1.5mV, referenced to 2.5V reference out
Input Range Limit for Auto-Zero Function
±10Volts/gain
Electrical
Excitation Voltage (Vdc)
5 to 30
Reverse Polarity Protection
-20V, on excitation line
Quiescent Current (mA)
15
Reference Out (Vdc)
2.50 ±0.05, referenced to ground
Output Voltage Limit (Vpk)
±2, referenced to 2.5V reference out
Gain Accuracy (%)
0.5
Output Impedance (Ω)
<50
Insulation Resistance (MΩ)
>100 @ 50Vdc
Environmental
Operating Temperature (°C)
-20 to +70
Storage Temperature (°C)
-20 to +70
Environmental Protection
IP50
Vibration (g)
20 pk from 50Hz to 2000Hz
Shock (g)
2000 pk with 3.6ms Haversine pulse
Physical
Case Material
Anodized Aluminum
Electrical Connector, Input
Binder Connector P/N 09-0098-00-05
(mates with Binder Connector P/N 99-0413-10-05)
Electrical Connector, Output
Binder Connector P/N 09-0098-00-05
(mates with Binder Connector P/N 99-0413-10-05)
Weight (grams)
34
1Auto-zero can be actuated using pushbutton or grounding remote auto-zero pin for minimum 2 sec.
Multiple actuations may be required to achieve the ±1.5mV limit.

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 4 of 11 t&[email protected]m
TM
Physical Configuration
The model 142 amplifier is packaged in a compact anodized aluminum housing and includes two Binder
connectors for the electrical interface. Two mounting holes are offered for the screw mounting option.
The top cover of the model 142 amplifier includes the following.
- A screw driver slot for the five selectable gain settings; x10, x50, x100, x200, x500
- A recessed push button to actuate the Auto-Zero function
Recessed push button to
actuate Auto-Zero function
Screw driver slot for
selectable gain settings
2x Binder connector series 711, part number 09-0098-00-05
Mates with Binder connector part number 99-0413-10-05

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 5 of 11 t&[email protected]m
TM
Mounting Installation
The model 142 in-line amplifier can be mounted with various methods. The three preferred methods of
mounting are as follows:
1. Screw mounting.
-The mounting surface should be flat, clean and free of any residue or foreign material.
-Torque screws to recommended limits below using steel washers under the heads of the
mounting screws.
2. Adhesive mounting.
-A silicone RTV is recommended for adhesive mounting of the amplifier.
-For removal, gently shear the amplifier loose from the mounting surface. Make sure not to use
excessive force as this may damage the amplifier.
3. Double-sided tape mounting.
-A strong double sided tape with acrylic adhesive is recommended (eg. 3M 444 series).
-For removal, gently shear the amplifier loose from the mounting surface. Make sure not to use
excessive force as this may damage the amplifier.
2x mounting holes for #4-40 or
M3 metric mounting screws.
Torque to 3 lb-in (0.3 Nm).

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 6 of 11 t&[email protected]m
TM
Humidity Protection
For model 142 amplifier has an ingress protection rating of IP50 (dust protection). It is not designed to be
used in any wet environments.
For installation in environments that could be subjected to falling water, it is recommended to install a
protective shrink sleeving around the housing of the amplifier. Temporary potting of the gain setting and
auto-zero cavities with silicone RTV are also recommended to provide additional protection. The mating
connectors will also need to be properly protected from falling water with adhesive and shrink sleeving.
Cable Attachment
The model 142 amplifier incorporates two Binder connectors mounted on each side of the housing. For
reliable operation it is recommend that a small amount of thread locking compound is used to secure the
connector plug during testing.
The cable assembly should also be properly secured at regular intervals during testing. It is
recommended to use clamps, wax, or tape to secure the cable to minimize cable motion that can add
noise to the output signal. The initial attachment should be within two to three inches of the amplifier with
some slack in the cable to prevent tension at the connector joint
Avoid routing cables near high-voltage wires and also ground the shield at the data acquisition to
minimize ground loops.
Calibration
A calibration certificate is provided with each model 142 that presents the actual gain at each gain
setting, and the actual values for the 5Vdc regulated supply output and the 2.5Vdc reference output. The
calibration cycle is one year.

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 7 of 11 t&[email protected]m
TM
System Installation
The model 142 amplifier is designed to be operated from 5-30Vdc excitation and provide a maximum
±2V full scale output (depending on gain setting) with a 2.5V reference voltage.
The amplifier is designed to be installed in a benign environment between the strain gage
instrumentation and the data acquisition system or recording instrument.
Measurement Specialties offers the following accessories that can be purchased with your equipment.
-Mating cable assembly model 379-XXX (-XXX in length in inches). This cable assembly is
ideally installed between the model 142 amplifier and the data acquisition system.
-Mating connector plug model AC-G04393 (Binder connector 99-0413-10-05). This connector
plug should be installed on the mating cable from the strain gage instrumentation.
The system installation is illustrated below.

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 8 of 11 t&[email protected]m
TM
Completion Resistor Installation
The model 142 is supplied with a 350 ohm completion resistor installed at the factory. This resistor can
be replaced by the user with another value if required to match that of the strain gage.
completion resistor
The leads of the completion resistor have been soldered to pads located on the top surface of the circuit
board at the factory. The user can replace the resistor by first removing the cover of the 142 which is
attached by four 0-80 cap screws. The user needs to follow standard industry practice in reflowing the
solder attachment using a soldering iron, cleaning residual flux, and taking the proper precautions for
ESD protection. Note that overheating the solder joints can damage the circuit. The leads of the
replacement resistor need to be formed and trimmed to fit the solder pads. Use the factory-installed
completion resistor as a template. The leads need not poke through the circuit board. The suggested
metal film resistor replacement is the Vishay Dale PTF56 series, ±0.1%, ±5ppm, 1/8W.
completion resistor
solder pads

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 9 of 11 t&[email protected]m
TM
Half Bridge Strain Gage Measurements
The model 142 can be wired for half bridge strain gage measurements if required. For this configuration,
the completion resistor will need to be replaced with a 0Ohm value. The wiring configuration for this
option is illustrated in the schematic below.
0Ohm completion resistor

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 10 of 11 t&[e-mail]
TM
Transducer Excitation
The amplifier offers two options for powering the desired transducer. A regulated 5.0 +0.0/-0.1 Vdc
supply is available on Transducer Pin 5. For other supply voltage requirements, Transducer Pin 1 should
be used which is the pass through power from the 5-30Vdc excitation source. This output is not regulated
and should be a clean supply to the transducer.
The wiring connection diagram is illustrated in the prior section.
Do not connect both Pin 1 and Pin 5 to the strain gage. Connect only one of the pins depending
on if the regulated 5Vdc power supply will be used or the pass through power from the excitation
source.
When using the 5Vdc regulated supply (Pin 5), the excitation voltage may need to be derated for a given
strain gage resistor value. The derating curve is illustrated below given an ambient temperature of 70°C.
For example, a 350 ohm strain gage (with matching completion resistor) cannot have an excitation
voltage applied to the 142 that exceeds 25.7Vdc.
There is no restriction on the pass through power (Pin 1).

Operating Manual
Measurement Specialties, Inc. www.meas-spec.com [phone]
32 Journey, Suite 150, Aliso Viejo, CA 92656 USA 11 of 11 t&[e-mail]
TM
Auto-Zero Function
The model 142 amplifier incorporates a unique Auto-Zero feature. The Auto-Zero can be actuated by two
methods.
1. Manually pushing the recessed Auto-Zero button on the top cover for a minimum of two seconds.
2. Remotely grounding the connection to Pin 5 of the Instrumentation output connector for a period
of two seconds minimum. To avoid inadvertent zeroing, the connection to pin 5 needs to be
isolated from grounding or extraneous voltage signals.
Multiple actuations may be required for the output to pull within the limit of ±1.5 mV. The amplifier can
auto-zero unamplified bridge offsets within a range of ±10 volts per gain. The bridge consists of the strain
gage and three fixed resistors. For example, a gain setting of X10 allows the correction of offsets from
the bridge within a range of ±1 volt. Conversely, offsets within ±20mV can be corrected given a gain
setting of X500. Note that the auto-zero correction factor is permanently retained until its next actuation
(ie. auto-zero can not be disabled).
If the gain setting on the amplifier is changed at any time or the transducer is replaced, the Auto-
Zero procedure needs to be re-actuated.