Information

Technical reference6

3 Technical reference

3.1

Capture modes

Three modes are available for capturing data:

BM_SINGLE: collect a single block of data and exit

BM_WINDOW: collect a series of overlapping blocks of data

BM_STREAM: collect a continuous stream of data

BM_SINGLE is useful when you wish to collect data at high speed for a short period:

for example, to collect 1000 readings in 50 milliseconds.

BM_WINDOW is useful when collecting several blocks of data at low speeds - for

example when collecting 10,000 samples over 10 seconds. Collecting a sequence of

single blocks like this would take 10 seconds for each block, so displayed data would

not be updated frequently. Using windowing, it is possible to ask for a new block more

frequently, for example every second, and to receive a block containing 9 seconds of

repeat data and 1 second of new data. The block is effectively a 10-second window

that advances one second per cycle.

BM_STREAM is useful when you need to collect data continuously for long periods. In

principle, it could be used to collect data indefinitely. Every time pl1000GetValues

is called, it returns the new readings since the last time it was called. The

noOfValues argument passed to pl1000Run must be sufficient to ensure that the

buffer does not overflow between successive calls to pl1000GetValues . For

example, if you call pl1000GetValues every second and you are collecting 500

samples per second, then noOfValues must be at least 500, or preferably 1000, to

allow for delays in the operating system.

3.2

Scaling

The PicoLog 1000 Series devices produce values in the range 0 to maxValue, where

maxValue is the value returned by the pl1000MaxValue function. To convert ADC

readings to volts, multiply by 2.5 and divide by maxValue.

For example, maxValue for the PicoLog 1216 is 4095. Therefore, an ADC reading of

132 from this device from a represents 132 x 2.5 / 4095 = approx. 0.0806 volts.