Why does my new Blood FlowMeter appear to output higher values than my old Blood FlowMeter?

There was an output specification change for the ML191/IN191 Blood FlowMeters in 2005/06. Below is a description of this change:
  • The original flowmeters were set to scale 2000 BPU per 1 V; while the current flowmeters are set to scale 1000 BPU per 1 V. 
  • The dynamic range was 0 - 9999 BPU on the original flowmeters; while it is now 0 - 5000 BPU for current flowmeters. This range is across 0 - 5 V in both cases.  
The current approach means that only half the potential dynamic range is accessible through the analog outputs, however there is a 2-fold increase in resolution. It is very unusual to see perfusion measurements of above 5000 BPU, which is why the change was made.

As a result of this change, each flowmeter type requires a different 2-Point Calibration using Units Conversion in LabChart. The following values should be used to ensure all flowmeters output relative BPU correctly:

Old Flowmeter (prior to 2006):
0 V = 0 BPU
5 V = 9999 BPU

Current Flowmeter (2006 and later):
0 V = 0 BPU
5 V = 5000 BPU

If the correct Units Conversion for current flowmeters (i.e. 0 V = 0 BPU; 5 V = 5000 BPU) is incorrectly applied to the old flowmeter types, then these older flowmeters will show 1/2 the expected BPU output in LabChart.

Specifications for the current Blood FlowMeter can be found HERE.