Low-g Accelerometer User Manual
Order Code: LGA-BTA
The Low-g Accelerometer can be used for a wide variety of experiments and demonstrations, both inside the lab and outside.
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.
Compatible Software
Choose a platform below to see its compatibility requirements.LabQuest
Interface LabQuest App LabQuest 3 Full support LabQuest 2 (discontinued) Full support LabQuest (discontinued) Full support Computers
Software Interface Graphical Analysis Logger Pro Logger Lite LabQuest Mini Full support Full support Full support LabQuest 3 Full support Full support Incompatible LabQuest 2 (discontinued) Full support Full support Full support LabQuest Stream (discontinued) Full support 1 Full support Full support 1 Go!Link Full support Full support Full support LabQuest (discontinued) Full support Full support Full support LabPro (discontinued) Incompatible Full support Full support Compatibility Notes
Chromebook
Software Interface Graphical Analysis LabQuest Mini Full support LabQuest 3 Full support LabQuest 2 (discontinued) Full support LabQuest Stream (discontinued) Full support 1 Go!Link Full support LabQuest (discontinued) Full support Compatibility Notes
iOS
Software Interface Graphical Analysis Graphical Analysis GW LabQuest Stream (discontinued) Full support Full support LabQuest 3 Full support 1 Full support 1 LabQuest 2 (discontinued) Full support 1 Full support 1 Compatibility Notes
Android
Software Interface Graphical Analysis Graphical Analysis GW LabQuest Stream (discontinued) Full support Full support LabQuest 3 Full support 1 Full support 1 LabQuest 2 (discontinued) Full support 1 Full support 1 Compatibility Notes
Arduino
Software Interface Arduino Vernier Arduino® Interface Shield Full support LabVIEW
Software Interface NI LabVIEW SensorDAQ (discontinued) Full support Vernier myDAQ Adapter Full support 1 Go!Link Full support LabQuest Mini Full support LabQuest Stream (discontinued) Full support LabQuest 3 Full support LabQuest 2 (discontinued) Full support LabQuest (discontinued) Full support Compatibility Notes
Texas Instruments
Software Interface EasyData DataMate TI-84 SmartView DataQuest TI-Nspire Software EasyLink Full support 1 Incompatible Full support 2 Full support Full support 2 CBL 2 (discontinued) Full support 3 Full support 3 4 Incompatible Incompatible Incompatible LabPro (discontinued) Full support 3 Full support 3 4 Incompatible Incompatible Incompatible TI-Nspire Lab Cradle (discontinued) Incompatible Incompatible Incompatible Full support Full support Compatibility Notes
Quick Start
- Plug the sensor into the interface (LabQuest 3, LabQuest Mini, etc.).
- Connect the interface to your device.
- If using USB, connect to the USB port on your computer.
- If using Bluetooth® wireless technology, click your interface type and then select your device.
- Prepare for data collection:
- Vernier Graphical Analysis®: Launch the app, if necessary, and click Sensor Data Collection.
- LabQuest® App: Choose New from the File menu.
The software will identify the sensor and load a default data-collection setup. You are now ready to collect data.
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Videos
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Calibrating the Sensor
Optional Calibration Procedure
You do not need to calibrate this sensor. Each sensor is calibrated prior to being shipped to you. The measurement being made by this sensor is complex and can be difficult to analyze, so be sure to read the Frequently Asked Questions below. In most experiments you can simply use the default calibration, but then use the software’s zeroing option and zero the sensor along the axes.
Most accelerometers, including this one, sense gravity as well as acceleration. This can make results more difficult to understand, but it provides an easy calibration method. Calibration may be done using the acceleration due to gravity. To calibrate the sensor for measuring acceleration in the horizontal direction, position the accelerometer with the arrow pointing down for the first calibration point. Define this as –9.8 m/s2 or –1g. Rotate the accelerometer so the arrow points up and use the reading for the second calibration point. Define this as +9.8 m/s2 or +1g. The accelerometer will then read 0 with no acceleration when held horizontally. If you want to calibrate for measuring acceleration in the vertical direction, follow the procedure above, but define the first calibration point as 0g or 0 m/s2 and the second point as 2g or 19.6 m/s2.
Specifications
|
Power |
30 mA @ 5 VDC |
|
Range |
±50 m/s2(±5g) |
|
Accuracy |
±0.5 m/s2(±0.05g) |
|
Frequency response |
0–100 Hz |
|
Resolution |
0.037 m/s2 |
|
Stored calibration |
slope: 22.924 m/s2/V intercept: –51.751 m/s2 |
Care and Maintenance
Do not wrap the cable tightly around the sensor for storage. Repeatedly doing so can irreparably damage the wires and is not covered under warranty.
How the Sensor Works
The Low-g Accelerometer senses acceleration using an integrated circuit (IC) of a type originally designed to control the release of air bags in an automobile. This IC is micro-machined with very thin “fingers” carved in silicon. These fingers flex when accelerated. They are arranged and connected like the plates of a capacitor. As the fingers flex, the capacitance changes, and a circuit included in the IC monitors the capacitance, converting it into a voltage. An external op-amp circuit amplifies and filters the output from the IC.
The Low-g Accelerometer measures acceleration along the line marked by the arrow on the sensor. Accelerations are normally measured in either meters per second per second (m/s2) or g’s. One g is the acceleration due to gravity at the Earth’s surface, or 9.8 m/s2. This accelerometer will measure accelerations in the range of –5g (-49 m/s2) to +5g (+49 m/s2). This is a range of accelerations which a human body could experience without damage. Many collisions will produce much larger accelerations. In fact, dropping the accelerometer on a hard surface from even a few centimeters can produce accelerations of 100g’s. The Low-g Accelerometer will not be damaged by accelerations up to 1000g.
Note that the Low-g Accelerometer also senses the effect of gravity. We use this to provide an easy way to calibrate the accelerometer. Also, it allows you to use the Low-g Accelerometer as an “Inclinometer” to measure angles. Its reading will change as its orientation is changed from horizontal to vertical. You can measure angles to the nearest degree.
The Low-g Accelerometer is based on the L1S344ALH from STMicroelectronics. It is designed to measure small accelerations with minimal electronic noise. The noise is typically on the order of 0.5 m/s2 peak to peak. The offset voltage (voltage output at 0 m/s2) will drift somewhat with temperature.
Frequently Asked Questions on Accelerometer Measurements
Since the accelerometer is sensitive to both acceleration and the Earth’s gravitational field, interpreting accelerometer measurements is complex. A useful model for understanding accelerometer measurements is a spring-based scale with a reference mass (or object) attached to the scale. If the scale is pointing upward (the usual orientation for such a device) the weight of the mass causes the spring to compress, and you get a non-zero reading. If you were to turn the scale upside down, the spring will be extended, instead of compressed, and we get a reading of the opposite sign. If you turn the scale so it points sideways, and keep it motionless, then the spring will just be at its relaxed length, and the reading will be zero. If you accelerated the scale toward the mass, then the spring would compress. If you accelerate the scale away from the mass the spring would stretch. In each case the scale is reading a value corresponding to the normal force on the mass. This reading can be made relative by dividing out the mass, giving units of N/kg, which is the same as m/s2. The accelerometer measurements can be interpreted in exactly this way.
Q: What does an accelerometer measure?
A: Normal force per unit mass.
Note that it’s not the net force per unit mass (which would be acceleration), but it is the normal force per unit mass. This somewhat unusual quantity corresponds with what a rider on a roller coaster feels during the turns. This interpretation is useful even for the scalar total acceleration value, which is
9.8 N/kg for a 3-axis accelerometer at rest, zero for one in free fall, and greater than 9.8 N/kg for one making a corner.
This normal force interpretation works even for a one-axis accelerometer being accelerated in a horizontal direction. The reading is non-zero as the test mass inside the device has to have a force applied to accelerate it. That’s just a normal force that happens to be horizontal.
When discussing the accelerometer reading, we can call it the Normal Force per Unit Mass, with units of N/kg.
Q: I thought the accelerometer measured acceleration!
A: Here we are being very careful to not call something an acceleration when it is not a kinematic acceleration. For example, an “acceleration” of 9.8 m/s2 for an object that remains at rest is clearly a problematic interpretation, yet that’s what the accelerometer reads.
You can correct the accelerometer reading to get a true acceleration by adding the component of the gravitational acceleration field along the direction of the sensor arrow. For example, if the axis of the accelerometer is pointing upward, then the gravitational component is –9.8 m/s2. The accelerometer reads
9.8 m/s2 when the arrow is upward and the device is at rest. By adding
–9.8 m/s2, we get zero, which is the correct acceleration. If the arrow is horizontal, then the reading is zero, but the gravitational component is zero, and we still have zero for the true acceleration.
Q: What about g-force measurements?
A: We avoid the term g-force because the quantity doesn’t have units of force. Instead, g-factor can be used as a simplified label for Normal Force per Unit Mass in axis labels and discussions.
You can see that the g-factor is then 1 for an object sitting at rest on a table, zero in free fall, etc. The g-factor is dimensionless. If the Normal Force is a vector, then so is the g-factor. g-factor is completely optional–it is just a shortcut to avoid a long name.
Troubleshooting
For troubleshooting and FAQs, see www.vernier.com/til/1410
Repair Information
If you have watched the related product video(s), followed the troubleshooting steps, and are still having trouble with your Low-g Accelerometer, contact Vernier Technical Support at support@vernier.com 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/LGA-BTA/#support
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.
The symbol, shown here, indicates that this product must not be disposed of in a standard waste container.
Contact Support
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