VBOX III User Guide
Page 14 of 30
15/07/2011
Analogue inputs
The VBOX III contains four differential 24bit analogue input channels with a maximum sample rate of 100Hz. Each channel has its own dedicated analogue to
digital (A/D) converter with all four channels being sampled synchronously to each other. The voltage range of the input channels is ±50volts. Note that unlike
the ADC03 module, the analogue channels in the VBOX III are not electrically isolated from each other.
The analogue input connector also contains voltage outputs that can be used to power external sensors. These are a
Vbatt
connection which is equal to the
VBOX input voltage level and a DC isolated
5 V Out
connection which is equal to 5V ±2%. Both
Vbatt
and
5V Out
connections are internally protected by
100mA thermal fuses. For connector pin configuration see page 16. A screw-terminal connector block is available as an option for easy connection of signal
pins.
Example connection of resistive type sensor using isolated 5v supply
Example connection of sensor with built-in regulator
Using the VBOX.EXE software, logging of the analogue channel data can be switched on or off. It is also possible to change the name of each input channel
and configure scale and offset values for calibration of sensors. A scale value of 1 and offset of 0 correspond to a channel reading in Volts DC. This means
that the value stored on the compact flash card for the channel will also be in volts. When using a sensor such as a load cell, it may be desirable to store a
reading in Kg. In this case, changing the scale and offset to suit the sensor data sheet allows the data stored onto the compact flash to be in Kg. When
changing settings for an analogue channel using the VBOX.EXE software, a live data view of the current channel is shown. The value shown is the value after
scale and offset is applied and can therefore be used to aid sensor calibration.
