Chapter 3 General Purpose Transducer Amplifier Module

Chapter 3 General Purpose Transducer Amplifier Module
DA100C - Differential Amplifier module
The differential amplifier module (DA100C) is a general purpose, single channel, differential
amplifier. The DA100C is designed for use in the following measurement applications:
Blood pressure (hemodynamics)
Physiological sounds
Displacement (linear or angular)
Temperature
Muscle strain or force (pharmacology)
Humidity
The DA100C has one differential input linear amplifier with adjustable offset and gain. The DA100C is
used to amplify low-level signals from a variety of sources. The DA100C has built-in excitation
capability, so it can work directly with many different types of transducers, such as:
Pressure transducers
Piezo sensors
Strain gauges
Wheatstone bridges
Accelerometers
Photocells
Microphones
Thermistors
Electrogoniometers
Compatible BIOPAC Transducers are:
TRANSDUCER
TYPE
TSD104A
Precision Pressure
TSD105A
Variable Range Force
TSD107B
High Flow Pneumotach
TSD108
Physiological Microphone
TSD117
Medium Flow Pneumotach
TSD120
Noninvasive BP cuff
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TRANSDUCER
TSD121C
TSD125 Series
TSD127
TSD130 Series
TSD137 Series
TSD160 Series
TYPE
Hand Dynamometer
Fixed Range Force
Low Flow Pneumotach
Goniometers & Torsiometers
Very Low Flow Pneumotach
Differential Pressure
MP Systems Guide
If the input signal is applied differentially between the VIN+
and VIN- inputs, the Input Signal Range can be centered on
any voltage from -10 volts to +10 volts with respect to GND.
If the signal is applied to a single input (with the other input
grounded), then that signal can range over the selected Input
Signal (pk- pk) with respect to GND.
The DA100C can be used to directly connect existing
transducers. The DA100C can be outfitted with connector
assemblies for easy interfacing to a variety of “off the shelf”
pressure transducers, force gauges, and strain gauges.
These transducer connector interfaces (TCIs) have pin plugs
on one side and the transducer mating connector on the other.
The following TCIs are available. Or you can use the TCI Kit
to make a custom adapter.
TCI100
Grass/Astromed transducers – 6 pin
TCI101
Beckman transducers – 5 pin
TCI102
World Precision Instrument transducers – 8 pin
TCI103
Lafayette Instrument transducers – 9 pin
TCI104
Honeywell transducers – 6 pin
TCI105
Modular phone jack connector – 4 pin
TCI106
Beckman transducers – 12 pin
TCI107
Nihon Koden transducers – 5 pin
TCI108
Narco transducers – 7 pin
TCI109
Fukuda transducers – 8 pin
TCI110
Gould transducers – 12 pin
TCI111
Liquid metal transducers – two 2mm sockets
TCI112
Hokansen transducers – 4 pin
TCIPPG1 Geer to PPG100C only — 7 pin
ZERO
ADJ
GAIN
500
1000
2000
5000
ON
FILTER
OFF
AC
DC
V+
SHIELD
VIN+
BR ID G E
GND
VINSHIELD
V-
DA100
VREF1
VREF2
REF
ADJ
Voltage References
The DA100C has two adjustable voltage sources (VREF1 and VREF2) for activating passive
sensors like pressure transducers, strain gauges, thermistors and photocells. The references can
be set anywhere from -5.0 to +5.0 volts. GND is at 0 volts. VREF1 and VREF2 track each
other with opposite polarity, thus a maximum differential of 10 volts is obtainable for driving
external transducers. For example, if VREF1 is set to +1.0 v (with respect to GND), then
VREF2 will automatically be set to –1.0 v.
The references can be adjusted using the REF ADJ potentiometer near the bottom of the
module. The voltage references can handle up to 20 mA sourcing or sinking to each other or
GND. Pay close attention to your sensor drive requirements so as to minimize overall current
consumption.
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Frequency Response Characteristics
Use the 10Hz LP lowpass filter for connecting the DA100C to most pressure, force, and strain
transducers (i.e., TSD104A, TSD105A, TSD120, TSD121C, TSD125 Series, and TSD130 Series).
Use the 300Hz LP lowpass filter for connecting the DA100C to devices with higher frequency output
signals (i.e., TSD107B, TSD108, TSD117).
Use the 5,000Hz LP lowpass filter for connecting the DA100C to devices with the highest frequency
signals, such as microphones and clamp signals (patch, voltage or current).
Modules are factory preset for 50 or 60Hz notch options, depending on the destination country.
See the sample frequency response plots beginning on page 186: 10Hz LP, 300Hz LP, 5000Hz LP
DA100C Calibration
A. Reference calibration
B. Amplifier gain calibration
C. Transducer calibration if applying physical variable
D. Transducer calibration if not applying physical variable
A. Reference Calibration
The REFCAL (see page 40) is used to check the reference voltage of the DA100C. The ref
voltage is used to provide excitation to passive transducers.
B. Amplifier Gain Calibration
Use the CBLCAL/C.
C. Transducer Calibration if applying physical variable
1. Plug transducer it into the DA100C.
2. Set the gain switch on the DA100C to the desired level.
3. Apply the physical variable to the transducer on the low end of your expected range.
4. Press on Cal 1 in the scaling window in AcqKnowledge.
5. Apply the physical variable to the transducer on the high end of your expected range.
6. Press on Cal 2 in the scaling window in AcqKnowledge.
7. Review the Input Voltage differential (provided in the scaling window as a consequence of
pressing cal 1/cal2) and adjust if necessary
If the Input Voltage differential is less than +/- 100 mV it may be appropriate to increase
the gain setting on the DA100C.
If either Input Voltage signal is higher than 9.9V or less than –9.9V, then reduce the gain
setting on the DA100C.
If you adjust the Gain switch setting on the DA100C, then you will need to repeat steps 3-7.
The physical variable for calibration varies based on the transducer type. See the appropriate
transducer specification for details:
TYPE
TRANSDUCER
TRANSDUCER TYPE
TSD104A
Precision Pressure
TSD121C
Hand Dynamometer
TSD105A
Variable Range Force
TSD125 Series Fixed Range Force
TSD107B
High Flow Pneumotach
TSD127
Low Flow Pneumotach
TSD108
Physiological Microphone
TSD130 Series Goniometers & Torsiometers
TSD117
Medium Flow Pneumotach
TSD137 Series Very Low Flow Pneumotach
TSD120
Noninvasive BP cuff
TSD160 Series Differential Pressure
™
™
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MP Systems Guide
D. Transducer Calibration if not applying physical variable
Use this procedure if you can’t easily generate the required physical variable changes in order to
calibrate the transducer.
1. Calculate the de-normalized calibration factor, VY.
a) Note the factory calibration constant (generally listed as “Output” in the transducer
specifications), expressed in the form of voltage/physical variable (V/P),
b) Multiply V/P by the reference voltage (RV) of the DA100C (2V factory preset).
c) Multiply the result [(V/P) * RV] by the Gain switch setting value on the DA100C.
2. Plug the transducer into the DA100C.
3. Press Cal 1 …this will generate VB in the Input Voltage box
4. Enter the ambient physical value in the Cal 1 Map/Scale window
5. Enter Cal 2 Input Voltage as VY+VB
6. Enter the ambient + delta physical value in the Cal 2 Map/Scale window
DA100C Specifications
Gain:
Output Range:
Frequency Response
Low Pass Filter:
High Pass Filter:
Input Voltage (max):
Noise Voltage:
Temperature Drift:
Z (Differential input):
CMRR:
CMIV—referenced to
Amplifier ground:
Mains ground:
Voltage Reference:
Signal Source:
Input Voltage Range
Weight:
Dimensions:
www.biopac.com
50, 200, 1000, 5000
±10V (analog)
10Hz, 300Hz, 5000Hz
DC, 0.05Hz
±200mV (protected)
0.11µV rms - (0.05-10Hz)
0.3µV/°C
2MŸ
90dB min
±10V
±1500 VDC
-10 to +10V infinitely adjustable @ 20ma (max)
(Factory preset to 2 volts excitation)
Variety of transducers
Vin (mV)
Gain
50
±200
200
±50
1000
±10
5000
±2
350 grams
4cm (wide) x 11cm (deep) x 19cm (high)
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