Mantracourt Electronics Limited
T24-SAf Fast Strain Gauge Acquisition Module User Manual
17
Power Supply / Battery
The acquisition module operates from 2.1 to 3.6 Volts dc so can be supplied from a variety of cells.
WARNING: It is important to note that the acquisition module is NOT reverse polarity protected!
WARNING: The maximum voltage is 3.6V!
Considerations When Selecting Batteries
Re-chargeable or replacement
This really depends on the application. Some applications where expected battery life with alkaline batteries
will be many years would probably not warrant the use of re-chargeable batteries. Re-chargeable batteries
have implementation issues such as how to connect to the charger, how to seal this connection if required, can
the batteries be re-charged at a convenient point in the operation of the device I.E between shifts and does
the voltage, when charging, exceed the maximum supply voltage of the acquisition module if so the inline
charging module will need to be fitted.
Required battery life
Driven by the application and mainly dependent on measurement rate and sample time. The operation would
normally require that the acquisition module is used in Low Power Mode to maximise battery life.
Size of
Choosing a battery will be influenced by how much space is available and what battery life is required,
generally the bigger the battery the longer it will last.
Operating temperature range
A batteries useable capacity is influenced by its operating temperature. Generally, the lower the temperature
the lower their ability to provide charge. Beware of the batteries specified operating range when considering a
particular battery technology.
Self discharge.
Batteries are chemical devices and have a shelf life which needs to be considered in application where long
battery life is required. Typically an Alkaline has a battery life of 5 years.
Internal Resistance of battery
Low internal resistance is important, the higher the resistance the less useful life of the battery is available.
This is due to voltage drops caused during the high current phase of the measurement cycle. In the case of a
T24-SAf strain gauge input module 300mA required for 250uS. Batteries with an internal resistance of less than
150mOhm will not require the additional inline capacitor module.
Connections to battery
For the same reasons internal resistance must be low it is important to keep any voltage drops from the battery
to the acquisition module as low as possible too. Care must be taken in selecting the connection method
between batteries and acquisition module. For example cables should be kept as short and thick as possible.
Environmental
Other considerations when selecting a connection method to the Batteries is the effect of vibration. A standard
battery holder is a poor choice in applications when the device can be subject to vibration. This is due to the
interruption of supply from the battery to the acquisition module caused when the spring arrangement holding
the battery to the terminal of the holder is defeated.
Corrosion of terminals must also be considered as this will also introduce resistance into the supply
connections. This could be overcome by ensuring the enclosure is sealed.
Optimising battery life
Battery life can be optimised by considering the following.
Use of low power mode.
Transmission interval.
Required Measurement resolution (Sample time).
Sleep / Wake configuration
Auto-Sleep duration.
