Vernier PAMP User manual

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When designing an experiment using the Power Amplifier, consider the following:
1. Input Signal - The Power Amplifier requires an input signal source to
function; it does not create any waveforms without input. Most commonly it is
used with a LabQuest or with any AC or DC signal source that does not
exceed 12 V, such as the Function Generator (FGEN-PAMP). The Power
Amplifier provides both current and voltage gain so that larger loads can be
driven than is possible with the signal source alone.
2. Output - The output of the Power Amplifier can be connected to a speaker, a
test circuit such as an RLC circuit, or any device that requires a controlled AC
or DC signal.
3. Current Sensor - The current sense port allows monitoring of the current
through the output stage of the Power Amplifier. Connect this to a LabQuest
or other Vernier interface.
Using the Product
Connections on the Power Amplifirer
The Power Amplifier has several connectors used to control and monitor the
output.
l3.5 mm Audio Port - The primary input is the 3.5 mm audio-style port on the
back panel.
lBTA Port - The secondary input is the BTA receptacle on the back panel that
serves as both an input from LabPro and as a current sense output.
lRed/Black Output Terminals - The two output terminals on the front panel are
used to connect the load circuit. The negative (black) terminal is connected to
ground via a 0.1 Ω resistor. The red terminal can range between ±10V.
The back of the Power Amplifier,
showing the Power Connector, the
Audio/LabQuest Connector, and the BTA
Connector
The front of the Power Amplifier,
showing the output terminals, the
Power Indicator LED, and the On/Off
Switch
Choosing an Input Signal for the Power Amplifier
The most common input signals for the Power Amplifier are a LabQuest or a
function generator. Other signal inputs to the Power Amplifier, including using a
LabPro, are described at www.vernier.com/til/15045.
Power Amplifier
(Order Code PAMP)
With the Vernier Power Amplifier, you can drive loads
with ±10 V and currents up to 1 A. It works with any
input waveform, including DC, sine, square, triangle,
and sawtooth waveforms. The Power Amplifier can
drive a variety of loads, such as speakers, lamps, small DC motors, and RLC
circuits. These circuits typically draw more power than the signal source can
deliver. The Power Amplifier makes it possible to drive these heavy loads.
lThis sensor works with LabQuest®and with most function generators.
lIt can provide a steady, linearly controlled DC output for driving loads like DC
motors, and precise AC waveforms for driving things like speakers
lCurrent is limited to protect against overload and shorting.
lThe current monitor function enables you to log real-time load current.
lThe class A-B Push-Pull Amplifier provides low distortion.
Note: Vernier products are designed for educational use. Our products are not
designed nor are they recommended for any industrial, medical, or commercial
process such as life support, patient diagnosis, control of a manufacturing
process, or industrial testing of any kind.
What's Included
lPower Amplifier
lPower Supply
l3.5mm audio cable for LabQuest control
lBTA cable for LabPro input and current sensing
Compatible Software
See www.vernier.com/manuals/pamp for a list of software compatible with the
Power Amplifier.
Getting Started
Some circuits require more current than can be delivered by the output of a
Vernier LabQuest or other signal sources. The Vernier Power Amplifier amplifies
an existing signal so that it can be used to drive a speaker, a coil, an RLC circuit, a
motor, a resistor for heating experiments, electrolysis apparatus or other
experimental apparatus. A list of suggested activities can be found at
www.vernier.com/til/15021.

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The Function Generator (order code FGEN-PAMP) comes with a BNC-mono
cable designed for use with the Power Amplifier.
Use the function generator’s controls to select the waveform and frequency you
wish to use in your experiment. When used with this input, the Power Amplifier
applies a factor of ten gain to the input signal. The input is DC-coupled.
Videos
View videos related to this product at www.vernier.com/pamp
Specifications
LabQuest Audio (3.5 mm connector) Input
lDC coupled between tip and sleeve of 3-conductor connector
lFrequency range DC to 15 kHz.
lOverall gain 10X
lInput impedance 10 kΩ.
BTA Analog Input
lDC coupled and has a total gain of 2X to the output.
lInput impedance is 50 kΩ.
lMaximum input ±12V without damage.
lThis input is on pin 1, or the yellow wire, of the BTA Cable (see
www.vernier.com/til/5457 for details)
BTA Current Sensing
lThere is a 0.1 Ω resistor between the black terminal and ground. Current
measurements are based on the voltage drop across this resistor.
How the Sensor Works
The Vernier Power Amplifier is a DC-coupled amplifier capable of delivering 1 A
at 10 V. In many applications, the amplifier will simply increase the amplitude of
the input signal. This is true for audio-frequency applications.
In other applications a much lower frequency output is desired. Since many audio
sources are not DC-coupled, the Power Amplifier includes a novel pulse-width-
modulated (PWM) input to create extremely low-frequency waveforms and DC
offsets. The output of the PWM section is added to the input of the amplifier. For
example, an experiment might demand a signal of a few hertz. A typical signal
generator cannot create an output at that frequency, but the Power Amplifier can
generate such a waveform when driven with the correct PWM signal.
Finally, a current-sensing resistor allows monitoring of the output current. This
signal is available at the current-sense output connector. When this output is
connected to an analog input of a LabQuest or LabPro, a calibrated, autoID current
sensor is detected by software.
Input DC Blocking
Some signal sources contain an undesirable DC offset. Since the Power Amplifier
is DC-coupled in order to produce DC signals, any offset will be amplified
Use Power Amplifier with LabQuest App
Power Amplifier connected to a LabQuest audio out connector
The Power Amplifier requires a LabQuest 3, LabQuest 2, or original LabQuest
with LabQuest App 1.2 or newer. (LabQuest App 1.3 or newer is recommended.)
Launch the LabQuest Power Amplifier App by selecting it in the home menu. If it
is not present in the home menu, see www.vernier.com/labquest/updates/ for
information on updating your original LabQuest.
The Power Amplifier App includes waveform options of sine, triangle, square
wave, ramp up, and ramp down and DC. For the sine, square wave, ramp, and
triangle waveforms, you can set the frequency with the keyboard, the up and down
arrow keys, and the slider. The slider provides an easy way to change the
frequency: tap to the right or left of the slider control to double the current setting,
or drag the control to change the frequency smoothly. The VDC control is only
used for the DC waveform.
The Power Amplifier App can be run simultaneously with LabQuest App. For
example, the current sense output of the Power Amplifier is used with the
LabQuest App, while the control of the Power Amplifier is retained by the Power
Amplifier App. To switch between them, choose each by name in the LabQuest
home menu. This way you can control the output of the Power Amplifier while
simultaneously recording the current in LabQuest App.
Use Power Amplifier with Function Generator
The Vernier Power Amplifier can be used with most function generators. Connect
the function generator to the 3.5 mm input using a mono connector only. A stereo
connector may enable the PWM features of the Power Amplifier with undesirable
results. When used with this input, the Power Amplifier applies a factor of ten
gain to the input signal. The input is DC-coupled.
Connecting a function generator to the Power Amplifier with a mono audio cord
The Vernier Power Amplifier can be used with most function generators. Connect
the function generator to the 3.5 mm input using a mono audio connector only.

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For the current sensor to read correctly, all of the current that passes through the
load must return through the black terminal. For this reason, loads that have a
ground connection will not allow reliable current measurements. In particular, do
not use a simple 10 V Voltage Probe (order code VP-BTA) with the Current
Sensor, because the Voltage Probe will ground part of the circuit. Instead, use a
Differential Voltage Probe (order code DVP-BTA).
Troubleshooting
For troubleshooting and FAQs, see www.vernier.com/til/1986
Accessories/Replacements
Item Order Code
Frequency Generator FGEN-PAMP
Accessory Speaker PAAS-PAMP
Repair Information
If you have watched the related product video(s), followed the troubleshooting
steps, and are still having trouble with your Power Amplifier , contact Vernier
Technical Support at [email protected] or call 888-837-6437. Support
specialists will work with you to determine if the unit needs to be sent in for
repair. At that time, a Return Merchandise Authorization (RMA) number will be
issued and instructions will be communicated on how to return the unit for repair.
Warranty
Warranty information for this product can be found on the Support tab at
www.vernier.com/pamp
General warranty information can be found at www.vernier.com/warranty
Disposal
When disposing of this electronic product, do not treat it as household waste. Its
disposal is subject to regulations that vary by country and region. This item should
be given to an applicable collection point for the recycling of electrical and
electronic equipment. By ensuring that this product is disposed of correctly, you
help prevent potential negative consequences on human health or on the
environment. The recycling of materials will help to conserve natural resources.
For more detailed information about recycling this product, contact your local city
office or your disposal service.
Battery recycling information is available at www.call2recycle.org
Do not puncture or expose the battery to excessive heat or flame.
alongside an AC waveform. To block unwanted DC signals, add a 1µF
non-polarized capacitor in series to the input.
Output Circuit
The Vernier Power Amplifier has an analog Class A/B push pull output section
that will drive currents up to 1 A at frequencies from DC to over 10kHz. It has a
soft current limit, intended as a safety net. Do not connect the Power Amplifier to
a load that would require more than 1 A. Load current can be calculated by
dividing the output voltage by the resistance of the load or dividing the wattage of
the load by the operating voltage.
The output is bipolar but not differential or balanced. In other words, the black
terminal is at approximately zero volts and the red swings positive and negative. A
current sense resistor of 0.1 Ω is between the black terminal and true ground.
Grounding Concerns
The Power Amplifier is not grounded through the external power connections, so
any external voltage source applied to the black terminal will find its way back to
ground through the LabQuest or LabPro. This is not of any concern when driving
floating loads (a load with only two leads and each connected ONLY to the Power
Amplifier terminals.)
Despite the ungrounded output, take care when driving any load that is part of
another electrical system, such as a robotic device or computer peripheral. If you
have any doubts about ground loops, connect the black Power Amplifier terminal
to your system ground. The Power Amplifier current sensor may give false
readings with two ground paths but this connection method reduces the chances of
any damage to your LabQuest or LabPro. Running the LabQuest on battery power
(and not connected to a computer host) also reduces the chance of ground currents
returning through the LabQuest. Any time your LabQuest or LabPro unit is
connected to a computer with a USB cable it is connected to that computer’s
ground which, in turn, is probably grounded to the building’s power system
ground through the AC plug.
Stability
The Power Amplifier output section uses distributed feedback to achieve accuracy
and DC stability. The feedback circuits have been designed to be stable with a
wide range of loads but highly reactive loads with very low resistance may present
a high enough Q to incite oscillation. When driving reactive loads you should
always have at least a few ohms in series. This is also good protection against an
over-current condition.
Current Sensor Output
The Power Amplifier contains a current sensor that can be read by a LabQuest,
LabPro, SensorDAQ, or Go!Link. Connect the supplied BTA cable between the
Power Amplifier and the interface. When the Power Amplifier is turned on, the
current sensor will be detected by the data-collection software. The bandwidth of
the current sensor is not as high as the amplifier since it is a trade-off between
noise and several other factors.

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[email protected] • www.vernier.com
Rev. 06//01/22
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