The VibWire-108 contains 8 independently configurable analogue output ports and they are used to represent the output signal

Each analogue output is of the range   0 - 2.5V DC and any analogue output must scale a result to within this range
Care should be taken to ensure that the output signal is scaled as close as possible to sensor range

For  example, Channel 0 is used to output a signal from a sensor with operating range of 1452 - 3176 Hz

It is not possible to set the output range of the DAC directly to represent the absolute range of the sensor and so it must be set
to cover the sensor range with the minimum overlap in order to obtain the highest resolution.  

a range of

0V = 1400 Hz  & 2.5V = 3200 Hz             so  CH0 LF = 1400   and    CH0 RA = 3200 - 1400 = 1800 Hz             

 will give the highest resolution for this example

 DAC Resolution output port = 16 Bit      so Frequency Resolution = 1800 / 65536 = 0.03 Hz

in practice accuracy of around 0.5 Hz can be achieved when connecting the VW-108 to an analogue data acquisition system
 after allowing for the losses due to the Digital-analogue and Analogue-digital conversion process. The 0.5 Hz measurement
 accuracy is achieved using the NDACS loggers.

Only when operating the VibWire-108 with an active analogue output port need the operating characteristics for the vibrating wire sensor be defined.

 For general purpose operations the analogue output should be set to represent the full operating range of the sensor.


Integration to NDACS 6000 Logger

 Example 2

A vibrating wire pressure sensor with operating frequency 400 Hz to 1000 Hz connected to channel 5 on the VW-108

and the analogue output is to be connected to an NDACS 6000 logger unit.

CH5 LF  = 400 CH5 RA = 600     ( where range = 1000 - 400)             and CH(0-7).RA is the range parameter.

the NDACS input channel range is to be set to 2.5 V

therefore 0V = 400 Hz and 2.5V = 1000 Hz

The NDACS will use the ‘Scaled Current’ process option    A = 1 B = 0 C = 2.5 D = 400 E = 1000

The data logger will scale the results over the full range  Resolution = 600/65536 = 0.01 Hz

In practice an measurement accuracy of 0.05 Hz will be achieved after allowing for losses in the analogue conversion process.