Instruction manual MQ20 / MQ40

Instruction manual MQ20 / MQ40
Metra Mess- und Frequenztechnik Radebeul
D-01445 Radebeul Meißner Str. 58
Tel. +49-351-836 2191 Fax +49-351-836 2940 Email: [email protected]
Instruction Manual
Charge Attenuator
MQ 20 / MQ 40
The output signal of sensitive piezoelectric transducers with charge output is often too
high to be processed with regular charge amplifiers resulting in overload. The Charge
Attenuators MQ20 and MQ40 are used to reduce the transducer sensitivity by 20 or
40 dB depending on the model. This allows to use the full dynamic range of a
piezoelectric sensor. Typical applications are shock measurements with piezoelectric
accelerometers or force measurements with piezoelectric force transducers.
The Charge Attenuator MQ20 reduces the charge output of a connected sensor by
20 dB. The resulting sensitivity at the MQ20 output is calculated as follows:
B MQ 20 =
BSensor Charge sensitivity of transducer
at MQ20 input
BMQ20 Charge sensitivity at MQ20 output
The Charge Attenuator MQ40 works in the same way but with 40 dB attenuation:
B MQ 40 =
BSensor Charge sensitivity of transducer
at MQ40 input
BMQ40 Charge sensitivity at MQ40 output
The attenuation is independent of the connected sensor provided that the capacitive
load at the input of the Charge Attenuator is below 3000 pF. This will be normally the
case since charge transducers are usually connected with less than 10 m cable which
corresponds to about 1 nF cable capacitance. The input load is calculated as follows:
CI = Ci Sensor + CCable
CI = 3000 pF
Ci Sensor
Capacitive load at
Charge Attenuator input
Inner capacitance of piezoelectric
sensor, typically 400..1600 pF
Capacitance of sensor cable,
typically 100 pF/m
The sensor is connected at via the BNC-socket marked as SENSOR. The other BNCsocket is the output which is connected to the charge amplifier, for instance Metra
Model M68D1:
Please make sure to use only low noise cables for the connection of input and output,
for instance the Metra cables Models 009 and 010. Only with low noise cables optimum resolution and accuracy will be reached.
Cables longer than 10 m are not recommended. If longer cables cannot be avoided, the
longer cable should be between sensor and Charge Attenuator.
Please do not exceed the maximum capacitance of 3000 pF to obtain the stated accuracy.
Technical Data
Attenuation (CI < 3000 pF)
- 20 dB ± 1 %
- 40 dB ± 1 %
Maximum input capacitance CI:
3000 pF
Frequency range:
0.1 Hz .. 50 kHz
Charge input, BNC socket (female)
Charge output, BNCsocket
Operating temperature range:
-20 .. 80 °C
Aluminum, connected to ground
Dimensions without socket :
72 mm x ∅24 mm
55 g
Limited Warranty
Metra warrants for a period of
24 months
that its products will be free from defects in material or workmanship
and shall conform to the specifications current at the time of shipment.
The warranty period starts with the date of invoice.
The customer must provide the dated bill of sale as evidence.
The warranty period ends after 24 months. Repairs do not extend the warranty period.
This limited warranty covers only defects which arise as a result
of normal use according to the instruction manual.
Metra’s responsibility under this warranty does not apply to any improper or inadequate
maintenance or modification and operation outside the product’s specifications.
Shipment to Metra will be paid by the customer.
The repaired or replaced product will be sent back at Metra’s expense.
Declaration of Conformity
Product: Charge Attenuator
Models: MQ20 and MQ40
It is hereby certified that the above mentioned product
complies with the demands pursuant to the following standards:
EN 50081-1
EN 50082-1
Responsible for this declaration is the producer
Metra Mess- und Frequenztechnik
Meißner Str. 58
D-01445 Radebeul
Declared by Manfred Weber
Radebeul, 3rd of August, 1997
Version: Nov 2015
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