1122
Technical Description
Probe identification is utilised on the D900-P, FD2-P, SD2-P, MD2-P and RD2 Doppler units.
This is to allow the control unit to identify which probe has been fitted. Fitting an obstetric probe
will disable the waveform output(s).
The FD2-P/SD2-P/MD2-P/RD2, with an obstetric probe connected, will display the probe
frequency whenever the probe is changed.
The FD2-P/SD2-P/MD2-P/RD2, with a vascular probe connected, will give a continuous
indication of probe frequency.
In the SD2-P, MD2-P and RD2 the frequency to voltage conversion factor is changed according
to the frequency of the connected probe and the gain setting, effectively rescaling the output.
4.5 Probe Identification
Active noise reduction is used to reduce the amount of "hiss" that is present. When a signal is
below a set level, the cut off point of the low pass filter is lowered effectively reducing the noise
level.
When a large signal is detected, the bandwidth is increased to allow the full range of the signal
to be heard at the loudspeaker.
4.6 Active Noise Reduction
To increase battery life within the FD2-P, SD2-P, MD2-P, FD1-P, FD3-P and RD2 units, the
microcontroller will turn the unit off after 3 minutes of no signal. The unit will also switch off
after 10 minutes regardless of signal presence. This function is disabled when it is connected
to a Printa which is printing in obstetric or vascular mode (not applicable to SD2-P, FD1-P or
FD3-P).
4.7 Intelligent Auto Shut Off (FD2, SD2, MD2, FD1, FD3, RD2)
The calibration pulses for the D900-P are of 1 and 2kHz irrespective of probe frequency. The
MD2-P and RD2 will output pulses of 0.05% and 0.1% of the frequency of the connected probe.
The MD2-P and RD2 have bi-directional calibration pulses to scale both forward and reverse
channels. The calibration facility is disabled when using gain settings other than x1.
4.8 Calibration Pulses
The D900-P has a fixed waveform conversion factor of 0.5V/kHz, whereas the SD2-P, MD2-P
and RD2 have a conversion factor determined by the probe fitted and the gain setting.
The use of a variable conversion factor results in the waveform output presenting a voltage that
is essentially constant regardless of the frequency of probe fitted for the same velocity signal.
4.9 Waveform Conversion
To Next Page
Loading...
Need help?
General
