Piezo Film Lab Amplifier
Charge or Voltage Mode Operation
BNC Input and Output
0.01 to 1000 mV/pC Sensitivity Range in Charge Mode
1M to 1G Input Resistance, -40 to 40dB Gain in Voltage
Mode
Multi-Pole, Low-Pass and High-Pass Filtering with -3dB
Frequencies Ranging from 0.1Hz to 100kHz
Internal Battery (2 x 9V) or external 24VDC Power Supply
Operation
Th
e
Pi
ezo
Fil
m
L
a
b
A
mp
lifi
er is a versatile preamplifier for use with Piezo electric sensor s. The electri c sign al
from the piezo film is generated within the electrod es of a capacitor. It is important to arrange an input that controls the rate
of charge leakage appropriately for the application. Simply connecting a piezo film element to the input of an oscilloscope will
usually create a high-pass filter that removes any low frequency content of the original pi ezo signal, and this can lead to
disappointment or incorrect evaluation of the material's true potential. This has led MEAS to develop a new low-cost Piezo
Film Lab Amp, specifically aimed at developers and engineers exploring the material. Both first-time users and seasoned
professionals will benefit from the wide range of sensi t ivity adjustment in either voltage or charge modes, and the functionality
of the hi
g
h- and low-pass filters.
FEATURES
• Wide Dynamic Range
• Charge and Voltage Modes
• Response to 0.1Hz
• Active HP and LP Filters
APPLICATIONS
• Low Frequency Dynamic Strain
• Pyroelectric Signals
• Audio-band and Acoustic Signals
• Machine Vibration
• Piezo Cable and Traffic Sensor Interface
performance specifications
ELECTRICAL
Supply Voltage Internal 2 x 9V Battery or External 24VDC (using the supplied 100-240VAC 50/60Hz
power supply unit)
Max Input Voltage 30V
Max Linear Output Swing ±4V (battery), ±5V (ext)
Voltage Mode:
Input Resistor Values 1M, 10M, 100M, 1G Ω
Gain 0 to +40dB in 10dB Increments with -40dB Switch
Noise 30mV rms (0.20 Vpp)typ, 1Hz to 100 kHz, 1G Input, +40dB (lower on battery power)
Charge Noise:
Feedback Capacitor Values 100pF, 1nF, 10nF, 100nF
Sensitivity Range 0.01 to 1000 mV/pC
Noise 20mV rms (0.13 Vpp) typ, 1Hz to 100kHz, 100pF, +40dB Gain (lo wer o n battery power)
ENVIRONMENTAL
Operating Temperature 0 to 50°C
Operating Humidity 5 to 95% RH Non-Condensing
Survival Temperature -20°C to +60°C, Power Off
Linearity <1%
Piezo Film Lab Amplifier Rev 1 www.meas-spec.com 10/14/2008
1 of 8
Piezo Film Solid State Switches
Piezo Film Lab Amplifier Rev 1 www.meas-spec.com 10/14/2008
Instructions description of controls
Mode Selector Switch
The setting of this switch determines whether the
amplifier is functioning in “charge mode” or “voltage
mode.” In charge mode, the input appears like a
short-circuit sensor and all charge that is generated
by the sensor glows into the input and appears on a
feedback capacitor within an op-amp circuit. In
“voltage mode,” the input appears like an open circuit
and no charge flows. The settings of the various input
and filter controls then modify the actual performance
in either setting.
Feedback Capacitance Selector (charge mode)
When the amplifier is operating in charge mode, this
control changes the sensitivity of the initial amplifier
stage. In typical use, it will be set to the value closest
to the sensor under test. Selecting a feedback
capacitance lower than that of the sensor will create
further apparent gain, while selecting a higher
feedback capacitance will reduce overall gain. A
quantity of charge applied to the input numerically
equal to the feedback capacitance value (for
example, 100 pC of charge, with 100 pF setting of
feedback capacitance) will generate one volt from the
initial stage, before further modification by the filters
and gain control.
Input Impedance Selector (voltage mode)
When the amplifier is operating in voltage mode, this
control changes the electrical resistance seen at the
input of the amplifier. For a given value of sensor
capacitance (C), different values of input resistance
(R) create different low-frequency response
characteristics. The simple RC filter network forms a
high-pass filter, which operates independently from
the low frequency selector switch. The influence of
this impedance selector must therefore be
considered separately from the low frequency
selector (see Appendix B).
2 of 8
Piezo Film Solid State Switches
Piezo Film Lab Amplifier Rev 1 www.meas-spec.com
description of controls (continued)
Input Attenuator Switch (voltage mode)
This switch allows the input signal to be attenuated
by 40 dB (linear factor of 100), when the amplifier is
operating in voltage mode. This can be useful in
cases where the open-circuit voltage being
monitored is very high, and would cause the output
voltage to clip. The setting of this switch does not
affect the in
p
ut im
p
edance seen b
y
the sensor.
Low Frequency Selector
The function of this control is to apply a multi-pole
high-pass filter to the signal. Frequencies below the
selected limit will be progressively attenuated. In
charge mode operation, the signal will be -3 dB
down (or approximately 0.7 X) at the selected
frequency. In voltage mode, the influence of the RC
filter must also be considered (see Input
Impedance Selector). Reducing the low-frequency
content of a signal may be useful when the signals
of interest are relatively high in frequency and low
in amplitude.
High Frequency Selector
This control applies a multi-pole low-pass filter to
the signal. It can be used in conjunction with the
Low Frequency selector to form a band-pass filter,
where noise outside a selected band of frequency
can be strongly attenuated.
Gain Selector
The purpose of this control is to allow selection of a
final gain to be applied to the output of the filter
stages. Selecting "0 dB" in voltage mode means
that the overall gain of the amplifier is zero dB
(linear 1X), when the Input Attenuator is also set to
"0 dB". The gain is adjustable in 10 dB steps up to
40 dB (linear 100 X).
10/14/2008
3 of 8
Piezo Film Solid State Switches
Piezo Film Lab Amplifier Rev 1 www.meas-spec.com
Appendix
Power Indicator
The green power indicator LED lights when the power switch is switched to "1" (ON position), using
either the internal batteries or when the external 24 V power supply is connected.
Batt Low
The red low battery LED lights when the voltage of the internal batteries falls below 8 V approx. When
the battery power is no longer sufficient for correct operation, neither "Power" nor "Batt Low" will be
illuminated when power switch is switched to "1".
Battery Compartments
The battery compartments are accessible from the
rear panel. To open a compartment, the battery tray
should be lifted up slightly, then pulled outwards.
Batteries can be left in the amplifier while it is being
operated on external power.
External Power Input
Just below the battery compartments lies the input
connector for 24 VDC (center pin +ve). Use only the
power supply provided with the amplifier.
Power Switch
This switches power (from internal batteries or from external 24 VDC supply) to the amplifier on or off.
To conserve battery life, power should be switched off when unit is not in use.
Input BNC
Signal input (for either voltage mode or charge mode operation) should be connected to the Input BNC.
Input voltage should not exceed 30 V, and this voltage should not appear across a sensor capacitance in
excess of 100 nF. The input adds approx 50 pF shunt capacitance, which must be borne in mind when
calculating RC filter frequencies for low-value sensor capacitance in voltage mode.
Output BNC
Impedance 50 ohms max. The output of the amplifier is intended to drive the input of an oscilloscope,
signal analyzer, or data acquisition system.
10/14/2008
4 of 8
Piezo Film Solid State Switches
Piezo Film Lab Amplifier Rev 1 www.meas-spec.com
Appendix
Appendix A: Filter response plots
Upper Limiting Frequency Con trol
-60
-50
-40
-30
-20
-10
0
10
1 10 100 1000 10000 100000
Frequency (Hz)
Magnitude (dB)
100KHz
10 kHz
1 kHz
100 Hz
10 Hz
Lower Limiting Frequency Control
-60
-50
-40
-30
-20
-10
0
10
0.01 0.1 1 10 100 1000 10000
Frequency (Hz)
Magnitude (dB)
0.1 Hz
1 Hz
10 Hz
100 Hz
1 kHz
10/14/2008
5 of 8
Piezo Film Solid State Switches
Piezo Film Lab Amplifier Rev 1 www.meas-spec.com
Appendix
Appendix B: Influence of Input Impedance selection
on low frequency response (voltage mode)
The table below shows the theoretical -3 dB frequency (in Hz) of the high-pass filter that is
formed when a sensor of capacitance listed in first column is connected to the specified
input impedance.
1 M 10 M 100 M 1 G
100 p 1592 159 16 1.6
220 p 723 72 7.2 0.72
470 p 339 34 3.4 0.34
1 n 159 16 1.6 0.16
2.2 n 72 7.2 0.72 0.072
4.7 n 34 3.4 0.34 0.034
10 n 16 1.6 0.16 0.016
22 n 7.2 0.72 0.072 0.0072
47 n 3.4 0.34 0.034 0.0034
100 n 1.6 0.16 0.016 0.0016
Note: the shaded cells have a -3 dB frequency that is below the range of the Low
Frequency Selector, and in this case, the Low frequency Selector will determine the
performance. In the case of the unshaded cells, the low frequency limit will be determined
either by the Low Frequency selector, or by the data above, whichever is the higher.
10/14/2008
6 of 8
Piezo Film Solid State Switches
Piezo Film Lab Amplifier Rev 1 www.meas-spec.com
included in package
1) Piezo Film Lab Amplifier:
2) Power Suppl y:
Input: 100-240VAC, 50/60Hz, 1.8A
Output: 24VDC 1A
Connector: IEC 60320 C14 (inlet)
3) Power Supply Cable/Plug
MUST BE ORDERED SEPARATLY
Connector: IEC 60320 C13
Regional Versions Available:
1007232-1 - Power Supply Plug, EU
1007232-2 - Power Supply Plug, UK
1007232-3 - Power Supply Plug, USA
1007232-4 - Power Su
pp
l
y
Plu
g,
Ja
p
an
10/14/2008
7 of 8
Piezo Film Solid State Switches
included in package
4) Accessories
(a) 2 x 9V Batteries, Type 1604A
(6LF22/6LR61/MN1604), Mercury and
Cadmium Free
(b) Piezo Sensor (modified SDT1-028K), p/n
1-1000288-1, 1m Shielded Cable, BNC
Connector
(c) BNC “Tee” adapter
(d) 2 x BNC Cable, 0.58m Nominal, Bare
End
The information in this sheet has been carefully reviewed and is believed to be accurate; however, no responsibility is assumed for inaccuracies. Furthermore, this information does no
t
convey to the purchaser of such devices any license under the patent rights to the manufacturer. Measurement Specialties, Inc. reserves the right to make changes without further notic
e
to any product herein. Measurement Specialties, Inc. makes no warranty, representation or guarantee regarding the suitability of its product for any particular purpose, nor doe
Measurement Specialties, Inc. assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liability, including without limitation
consequential or incidental damages. Typical parameters can and do vary in different applications. All operating parameters must be validated for each customer application b
y
customer’s technical experts. Measurement Specialties, Inc. does not convey any license under its patent rights nor the rights of others.
ordering information
North America
Measurement Specialties, Inc.
1000 Lucas Way
Hampton, VA 23666
Sales and Customer Service
Tel: +1-800-745-8008 or
+1-757-766-1500
Fax: +1-757-766-4297
Technical Support
Email: piezo@meas-spec.com
Europe
MEAS Deutschland GmbH
Hauert 13
44227 Dortmund
Germany
Sales and Customer Service
Tel: +49 (0)231 9740 21
Technical Support
Tel: +49 (0)6074 862822
Email: piezoeurope@mea s-spec.com
Asia
Measurement Specialties (China), Ltd.
F1.6-4D, Tian An Development
Compound
ShenZhen, China 518048
Sales and Customer Service
Tel: +86 755 8330 1004
Technical Support
Email: piezo@meas-spec.com
Piezo Film Lab Amplifier Rev 1 www.meas-spec.com 10/14/2008
8 of 8