Spacelabs Medical, Inc.

Tektronix, Inc.

James R Brooks

Theodore G Nelson

Warren Woo

A circuit for use in a DMM utilizes an auxiliary A/D converter to measure the battery voltage of the DMM and displays the result on the LCD display screen of the DMM. The user receives a numeric indication of the battery voltage measured, rather than a simple good/bad or bar graph indication. The voltage measured provides the user with a quantitative indication which allows the user to determine how close the battery is to being exhausted. Thus, the user can be made aware of a weakened state of the battery before operation of a backlight further drains the battery to an unacceptably low level.

Apparatus for use in a DMM for measuring the battery voltage of the DMM

A method by which a microprocessor based handheld multi-meter, or other handheld electronic instrument, can communicate with a computer or other microprocessor based device through the measurement input jacks of the handheld multi-meter. A handheld meter, thus equipped, can receive control or calibration data from, and provide test or calibration data to, a host computer or microprocessor based accessory or other instrument. To enable this capability, the handheld meter employs dual-signal, single-axis jacks, for example split banana jacks, for one or more of its signal and ground receptacles. The handheld meter and the computer, or another microprocessor based instrument or accessory device that the meter is to communicate with, are equipped with mutually compatible software and appropriate hardware to support single signal path communication.

Instrument communication through signal jacks

A digital high-pass filter derived from a digital low-pass filter of conventional design. The digital low-pass filter periodically calculates respective low-pass filter output values. Corresponding high-pass filter output values are then calculated by subtracting the low-pass filter output values from input samples provided by digitizing an input signal. The high-pass filter output values are then used to generate samples which are applied to a digital-to-analog converter for outputting a high-pass filtered replica of the input signal. The digital high-pass filter compensates for sudden, relatively large changes in the input signal by comparing the low-pass filter output value to the input sample and, in the event that there is a large discrepancy therebetween, setting the low-pass filter output value to the input sample before calculating the high-pass filter output value.

Digital high-pass filter having baseline restoration means

A fast response, low-pass filter comprising a slow response low-pass filter and a fast response low-pass filter. Both of these low-pass filters receive an input signal, and their respective outputs are compared to each other. When the output of the slow response filter differs from the output of the fast response filter by a predetermined value, the response time of the slow response time filter is increased so that it can more rapidly follow the input signal. The fast response time low-pass filter can be implemented with either analog low-pass filters or by digital low-pass filters.

Fast response low-pass filter

An automatic blood pressure monitor having a blood pressure cuff, an air pump applying pressurized air to the cuff, an air valve selectively venting the cuff, and a pressure transducer generating an output signal having a D.C. component indicative of the steady-state pressure in the cuff, and an A.C. component indicative of oscillometric pulses. The pressure transducer output is amplified and applied to an analog-to-digital converter which generates a digital word indicative of the steady-state cuff pressure. The amplified pressure transducer output is also applied to one input of a differential amplifier having an output that is applied to an analog-to-digital converter having a limited operating range. The other input of the amplifier receives an offset signal from a voltage source to offset the amplified pressure transducer output so that the output of the differential amplifier will not exceed the operating range of the analog-to-digital converter.

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Beaverton, OR, United States of America

James R Brooks