LOAD CELL TYPES
Three types of load cell are manufactured by Geosense
- Vibrating Wire (VW)
- Strain gauge
- Hydraulic (Manometer or VW Transducer)
The factors to take into account when deciding which load cell type to use include
- Duration of monitoring
- Accuracy required
- Data logging requirement
Vibrating wire (VW) load cells
VW load cells are the most robust and suitable for civil engineering applications. Bearing this in mind, VW load cells certainly are our first choice for loads of 1000 kN and bigger. Sensors used are electromechanical and mechanically attached in the sensor, so they are very stable over the long term. Due to the fact that each load cell has either three or six gauges, individually read, eccentric loading is easily spotted. In terms of accuracy, VW load cells are the equal of strain gauge load cells. VW load cells cannot be dynamically monitored.
Output signal from VW load cells: Hz or Digits; Ω for thermistor if in place.
Hydraulic load cells
These are the least accurate as they are significantly affected by temperature. Hydraulic load cells are useful for monitoring anchors on long-term projects where any changes in load are likely to be significant. They can be upgraded to be data logged by attaching a Vibrating Wire (VW) or analogue pressure sensor. When fitted with a Bourdon gauge, they provide quick and simple readings.
Standard output from hydraulic load cells: manometer for pressure indication.
Strain gauge load cells
Should be used if dynamic monitoring is required. This is because they give a constant output and do not have to be polled for information. Strain gauge load cells are very accurate over the short term but may be prone to drift in the long term. This is due to glue drift of the attached sensors but also down to electrical drift of the sensors and other electronic components. They can be easily and cheaply data logged and are, arguably, the easiest and cheapest to use for wireless monitoring applications.
Output signal from strain gauge load cells: mV/V; Ω for thermistor if in place.
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