Product Notes
The Bridge120 data logger is designed to interface with and measure strain gauges and load
cells. The device provides an excitation voltage of 2.5V’s and is available in the following
millivolt input ranges: ±10mV, ±25mV, ±100mV, ±1000mV. The Bridge120 features a
sampling rate of up to 20Hz.
LEDs
Once started, the LED will flash at the selected reading rate to indicate the device is running.
Configuring the Data Logger
Voltage Divider Configuration
The Voltage Divider configuration is a frequently used setup to measure bridge strain.
1. Jumper between POWER and REF+
2. Place a 12k resistor between REF+ and REF-
3. Jumper between REF- and IN+
4. Place the strain gage between IN+ and IN-
5. Jumper between IN- and GROUND
Conversions
To convert the Voltage values into Ohms, use the following formula:
Example: The MadgeTech software reports a voltage of 20mV in the circuit described above.
The strain gage resistance is therefore:
The resistor Ro between REF+ and REF- and the strain gage value form the mV reference
(mVref). This may be expressed as:
The Bridge120-25 has a resolution of about 2µV. If the resistance of the strain gage
changes by +.1, the device would measure a change of approximately +20µV. Conversely,
this voltage resolution translates in Ohms to approximately:
Note: The maximum voltage must be kept within the specified input range. See data sheet for details.
Installation Guide
Installing the Interface cable
- IFC200
Insert the device into a USB port. The drivers will install automatically.
- IFC110
Plug the serial cable into the port and verify it is secure.
Installing the software
Insert the Software USB into an open USB port. If the autorun does not appear, locate the
drive on the computer and double click on Autorun.exe. Follow the onscreen instructions.
Connecting the data logger
- Once the software is installed and running, plug the interface cable into the data logger.
- Click the Communication Menu, then Auto Configure Port.
- After a moment, a box will appear stating a device has been found.
- Click OK. The Device Status box will appear. Click OK.
- At this point, communications have been configured for your logger. These settings can
be found under the Communication Menu.
Device Operation
Starting the data logger
- Click Device Menu then Start Device.
- Choose the desired start method.
- Choose the start parameters by selecting a Reading Rate suitable for your application.
- Enter in any other desired parameters and click Start.
- A box will appear stating the data logger has been started. Click OK.
- Disconnect the data logger from the interface cable and place it in the environment.
Note: The device will stop recording data when the end of memory is reached or the device is stopped. At this
point the device cannot be restarted until it has been re-armed by the computer.
Downloading data from a data logger
- Connect the data logger to the interface cable.
- Click the Device Menu then Read Device Data. This will offload recorded data onto the PC.
Device Maintenance
Battery Replacement
Materials: Small Phillips Head Screwdriver and a Replacement Battery (LTC-7PN)
- Puncture the center of the back label with the screw driver and unscrew the enclosure.
- Remove the battery by pulling it perpendicular to the circuit board.
- Insert the new battery into the terminals and verify it is secure.
- Screw the enclosure back together securely.
Note: Be sure not to over tighten the screws or strip the threads.
Recalibration
Bridge120 standard calibration values:
Product Quick Reference Card
POWER
REF +
REF -
IN +
IN -
GROUND
Ro=12kΩ
Strain Gauge Rsg
Bridge120
Logger Voltage 10mV 25mV 100mV 1000mV
Strain (V) 0V and
9-10mV
0V and
22.5-25mV
0V and
90-100mV
0V and
900-1000mV
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