Transonic TS420 - TS420 Flowprobe Zero Offset and Scale Setting

22 AU-OPR-400Ser-EN,
Rev D
C. Flowprobe Zero Offset
If there is any zero offset, it can be nulled using the [Zero Adj] button. Use a pointed instrument (such
as the tip of a pen or stylus) to depress the button. Make sure the Probe is fully wetted before adjusting
the zero offset as dry Probes display more signal drift. NOTE: Small zero offset is normal due to slight
differences in the transducers and generally considered insignicant.
1) For applications where an absolute zero is required, nullify the zero offset on the vessel of interest.
Temporarily occlude the vessel to stop ow and then depress the [Zero Adj] button. NOTE: Once the
zero offset has been adjusted, it cannot be adjusted again unless the Probe is disconnected or the
Module turned off. Turning off the Module or disconnecting the Probe will reset the zero offset.
D. Determining Scale Setting
The ow range of each Flowprobe is scaled according to Probe size (see Flowprobe Specication Table,
RL-20-ds, for scale factor values). Each Flowprobe has two scale ranges: normal ow and low ow. Low ow
range is 1/4 of normal range, however the signal is amplied to provide a four fold increase in sensitivity.
The scale factor value is the ow at 1 volt output in mL/min or L/min. Probes measure bidirectional ow up
to ve times the scale factor value.
When determining which scale setting to use it is important to keep in mind that under normal
physiological conditions for a given vessel size, mean blood ow values are generally near or below the 1
volt normal scale value for the appropriate Probe size for the vessel.
● Peak pulsatile ows may push the output to 5 volts.
● Beyond the 5 volt maximum range of the Module, “peak clipping” occurs and the complete wave form is
not recorded and the mean ow may be underestimated.
● Use the low ow range setting ONLY when peak ow will not exceed 5 times the low ow scale factor. It
is recommended to check peak ows using the normal ow mode before switching to low ow if there is
concern about potential peak clipping.
Put the Flow Module in [Scale] mode to display the value of the Probe’s 1 volt reference signal in the
normal or low ow range. This reference signal is used to calibrate the data acquisition system and does
not change the factory calibration of the Flowprobe. All Transonic
®
Flowprobes are precalibrated at the
factory for absolute volume ow measurement. (See Calibration Technical Note RL-5-tn).
E. Calibrating a Data Acquisition System
1) Connect the data acquisition system to either the front or back analog outputs.
2) Follow the data acquisition provider’s instructions for a 2-point calibration.
3) For reference point “zero” (0 volts), press [Mode] to select “Zero” and record the output voltage.
4) For reference point “1 volt”, press [Mode] to select “Scale” and record the voltage. The value of the 1
volt reference signal is displayed on the digital display of the Module while the analog display shows 1V.
5) If the scale is changed (Standard Flow vs. Low Flow) during the experiment, the 1 volt reference scale
value in the data acquisition system must be reset. Repeat the above sequence whenever the ow range
setting has been changed.
TS420 Module: Functional Tests