Strain gauge measurement is one of the big challenges for sensor
technology, especially the weighing industry. Due to the small
excitation of the strain gauges on a load cell of only 0.2 % (2000 ppm)
and due to the high resolution of 16 Bit and more, the resistors must be measured with a precision deeply in the ppb range. Reasonably, this can only be done measuring the ratio of the resistors.
Here the PICOSTRAIN measuring principle is breaking new grounds compared to A/D converters. The ratio of the resistors is ascribed to a time interval measurement, not to a voltage difference like in Wheatstone bridges. The sensor's resistors together with a capacitor act as low-pass filters. The capacitor, charged to Vcc, is discharged through the sensor's resistors. The discharge time to trigger level (selectable) is precisely measured by a TDC (Time-to-Digital Converter).
General Circuit Features
The PICOSTRAIN integrated circuits are realized without any analog component. Again, acam uses its TDC technology to set new standards in circuit design and takes the advantages of this principle like: