An RMS converter has first and second transistors (40a and 42a) providing a signal representing double the log of the input voltage, a third transistor (40b), matched with the first (40a), providing a signal representative of the log of the output voltage and a fourth transistor (42b), matched with the second (42a). providing a signal representative of the anti-log of the ratio of those signals; the transistors in each matched pair are repetitively interchanged functionally thereby reducing errors caused by slight differences in the transistor operating characteristics.
A sampled data, analog computing method and circuit for producing an output voltage V.sub.OUT with a magnitude proportional to the root-mean-square value V.sub.RMS of a monopolar input voltage V.sub.DC, first demodulates or chops a time-varying monopolar input voltage V.sub.DC of interest to produce a demodulated or chopped voltage V.sub.CHOP, and then filters the chopped voltage V.sub.CHOP to produce an output voltage V.sub.OUT. The chopping operation is conducted at a duty ratio or modulation ratio proportional to the ratio of the monopolar input voltage V.sub.DC to the output voltage V.sub.OUT, with the result that the magnitude of the output voltage V.sub.OUT is proportional to the root-mean-square value V.sub.RMS of the monopolar input voltage V.sub.DC. The illustrated embodiment of the invention (i) rectifies a time-varying bipolar input voltage V.sub.AC of interest with a precision fullwave rectifier to produce the monopolar input voltage V.sub.DC, (ii) produces a pulse code modulated (PCM) signal with the required duty ratio utilizing an oversampling delta-sigma modulator, and (iii) produces the output voltage V.sub.OUT with an inverting second order low pass filter so that V.sub.OUT has the inverted polarity and greater magnitude compared to V.sub.DC that is required on the delta-sigma modulator reference node.
A rectifier circuit is disclosed in which the levels of an input signal and a reference signal are compared, and the polarity of the equivalent resistor is set at positive or negative depending on the result of the comparison. The equivalent resistor is connected, as an input resistor, to a differential amplifier. A feedback resistor is connected between the input and output of the differential amplifier. This arrangement enables the rectifier circuit, with only a single differential amplifier, to perform the rectifying operation with a gain.
An rms converter accommodates incoming signals of large crest factor by using an amplifier having a transfer function of non-uniform slope. The amplifier has a lower gain for larger signals. The output of the amplifier is converted to digital voltage values. The non-uniform gain of the amplifier is compensated for in digital calculations of the rms value. The invention produces accurate rms measurements by accurately measuring lower incoming signal voltages while still accommodating high peak voltages. The invention also reduces the dynamic range requirements for the analog to digital converter.
A pressure-sensitive adhesive closure for a disposable diaper can exhibit high peel resistance both at low and high speeds while its peelability at high speeds is not excessively shocky when it employs a pressure-sensitive adhesive of a certain rheology and it has, covering the fastening area, a polyolefin layer having microtopographical features as in FIGS. 1-6 of the drawing. As seen in FIGS. 1-6, suitable microtopographical features are provided by a large number of closely spaced asperities at least two micrometers in height that have a jagged appearance at 500.times.. A pressure-sensitive adhesive of suitable rheology can be provided by a blend of an AB block copolymer, such as a copolymer of styrene and either isoprene or butadiene, and tackifying resin, preferably a mixture of liquid and solid tackifying resins.
