Instrumentation Selection Guide Definitions
Excitation
A Wheatstone bridge-based sensor, such as a load cell, requires excitation voltage to operate. The excitation voltage is typically 10V; however, many instruments supply lower voltage, an 2.5V, 5V, and others. Since these sensors are ratiometric, Interface instrumentation devices are designed to pair with these types of sensor products.
Signals
The output signal from a load cell is expressed in terms of mV output per V of excitation, at capacity. For example, a 100 lb capacity load cell rated for 2 mV/V output will have 20mV output at 100 lb, when excited with 10V. Because the output signal is directly affected by input voltage, it’s important to maintain a stable excitation voltage, which our instrumentation does.
Signal Conditioners
A signal condition provides stable excitation voltage to the sensor and amplifies the low-level sensor signal to a high-level output such as +/-5V, +/-10V, 0-20mA, 4-20mA, 0-5V, or 0-10V.
Many of our products include filtering, which can help reduce noise in the output signal.
Data Acquisition Systems
A complete data acquisition system consists of DAQ hardware, sensors and actuators, signal conditioning hardware, and a computer running DAQ software. Interface provides DAQ instrumentation that are ideal for completing a sensor-based system. Many data acquisition systems require high-level inputs such as +/-10V and don’t work very well with low level mV signals. Interface instrumentation solutions do work well with DAQ systems. The DAQ doesn’t necessarily supply a stable excitation voltage like the Interface sensors do.
Interface Modules
An interface module converts the low-level mV/V sensor signal to a digital format that can be transmitted to a computer, (PC or laptop). Popular interface modules provide USB, wireless USB, or Bluetooth data transmission. Software is normally provided and allows data display, logging, and graphing. The interface modules are commonly used when data needs to be logged to computer and you are not using an existing data acquisition system. The interface module advantages over standard data acquisition are ease of use and they are normally plug-n-play. Considerations when selecting this type of instrumentation include bit resolution, number of channels, sample rate, software features and type of output.
Indicators
Interface indicators provide stable excitation voltage and converts the sensor signal to a digital display. Commonly available features include analog or digital output, selectable digital filtering, peak and valley monitoring and set point outputs. Things to consider when selecting an indicator are internal sample rate and update rate of analog output.
Wireless Telemetry System (WTS)
Wireless is very popular today. Interface’s Wireless Telemetry System is easy-to-use providing wireless data communication between a load sensor and a receiving indicator. The WTS is capable of receiving multiple inputs and is fully compatible will all Interface force sensors. The WTS comes calibrated, tested and ready-to-run. The charge lasts up to three months using AA batteries.
