Philips M1353A manual Front End Board, M1351A M1353-66501 M1353-66511, M1353-66512

Front End Board

Front End Board

M1351A (M1353-66501 and

M1353-66511)

The Frontend board (M1353-66501 − single, M1353-66511 - dual) contains the analog circuitry for measuring all the possible parameters of the M1351A. One IC on the board provides the US timing and window control. Each type of transducer has a specific mode resistor which is recognized by the M1351A when the transducer is connected to an input socket. In this way, the user can be warned if a wrong transducer is connected. The marker cable is also connected to the Front End Board.

The frontend boards used with software at Rev E and higher are triangular in shape, not rectangular.

Ultrasound

The ultrasound transducer transmits 998.4kHz ultrasound bursts which are generated by the digital control ICs. The burst widths are controlled by software. The transmitter amplifier supplies 5Vpp_ at the Cardio sockets. The repetition rate is 3.2kHz. The received 998kHz signal is amplified by a high frequency amplifier with a gain of 120 and then split to provide a reference path a and a compare path b. The two demodulators a and b are independently controlled by software in their receive windows by the control ICs. The demodulated LF signals are bandpass filtered (100 to 450Hz) and amplified by a software controlled gain of 180 to 1860 in eight steps. The FMP-LF path is independently demodulated, bandpass filtered and amplified by a factor of 18.

Toco

The excitation voltage is a biphase 2.4kHz rectangular continuous wave with an amplitude of 5Vpp. The frequency is generated in the control chip by dividing the 4MHz system clock.

the sense input is amplified by 786 (5∝ ;V/V/mmHg), rectified with a synchronous detector and lowpass filtered with a cut-off frequency of 7.5Hz.

M1353A Used in monitors with serial number prefix ≤ 3652G.

(M1353-66512)

The Frontend board contains the analog circuitry for measuring all the possible parameters of the M1353A. An IC on the board provides the US timing and window control, and

52 Chapter 6 Theory of Operation