Signal converter

In a signal converter comprising an operational amplifier having an inverting input, a non-inverting input and an output, the input signal to the non-inverting input being an actual signal to be converted, means coupled to the output of the operational amplifier for providing a correctional signal input to the inverting input of the operational amplifier comprising:

• (a) a first lowpass filter coupled to the output of the operational amplifier;
• (b) a second lowpass filter coupled to the non-inverting input of the operational amplifier;
• (c) a first summing point having an output and first and second inputs coupled to the first and second lowpass filters respectively for comparing a mean signal value output of the first lowpass filter with an analog signal value output of the second lowpass filter;
• and
• (d) an integrator coupled to the inverting input of the operational amplifier and to the output of the first summing point, the integrator providing the correction signal input to the inverting input of the operational amplifier.

In a signal converter comprising an operational amplifier having an inverting input, a non-inverting input and an output, means coupled between the non-inverting input and the output of the operational amplifier for scaling a signal input to the non-inverting input of the operational amplifier, the scaling means comprising:

• (a) a microprocessor coupled to the output of the operational amplifier for sampling the output of the operational amplifier, comparing the sampled value with a reference signal value, and providing an output signal indicative of a measuring range;
• (b) a gain selection circuit coupled to the output signal of the microprocessor;
• (c) an amplifier coupled to the gain selection circuit and to a reference signal input for providing a scaling signal output;
• and
• (d) a summing point having a first input being the signal to be scaled, a second input being the scaling signal output of the amplifier, and an output being the scaled signal input to the non-inverting input of the operational amplifier.

A method for scaling a signal input to a signal converter, the signal converter for converting the input signal to a pulse width modulated output signal coupled to a first input of a microprocessor, the scaling method including the steps of:

• sampling the pulse width modulated output signal at a predetermined frequency to determine a signal value;
• comparing the signal value result of the sampling with a reference signal value;
• calculating an actual signal value measuring range from the result of the comparison;
• providing an output signal indicative of the actual signal value measuring range to a gain selection circuit for an amplifier;
• establishing a scaling level at the output of the amplifier responsive to the gain selection circuit;
• and
• scaling the signal input to the signal converter responsive to the scaling level output of the amplifier.

In a signal converter comprising means for converting an input signal to a pulse width modulated output signal, a method of scaling the input signal to the signal converter including the steps of:

• (a) sampling the pulse width modulated output signal at a predetermined frequency resulting in a signal value;
• (b) comparing the signal value result of the sampling with a reference signal value;
• (c) establishing a scaling level responsive to the comparison;
• and
• (d) substracting the scaling level from the input signal to the signal converter.