Smart frequency-code converter with enhanced survivability
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SMART FREQUENCY-CODE CONVERTER WITH ENHANCED SURVIVABILITY
V. V. Makarov
UDC 621.317.72
A smart three-channel frequency-code converter with enhanced survivability is discussed. Self diagnostics and self calibration of the converter are performed without interruption of ongoing conversions. Keywords: smart converter, adaptation, self diagnostics, self calibration, survivability.
Frequency-code converters are used in automatic control systems and measurement-data systems for converting the frequency of output voltages from sensors for physical quantities into binary codes. A four-channel smart frequency-code converter has been discussed in Ref. 1. It adapts to unknown frequencies of input frequency signals, performs self diagnostics and self calibration, and is powered by a USB bus. The disadvantages of the smart frequency-code converter (SFCC) include low survivability and the interruption of ongoing conversions during periods of self diagnostics and self calibration. When one of the converter channels fails, the SFCC no longer works and must be replaced. The time taken for self diagnostics and self calibration corresponds to several tens of ongoing conversions, and this may be unacceptable. This article deals with a way to eliminate these shortcomings of the SFCC. To do this, one of its working converter channels is turned into a backup channel and the structural diagram is modified. The number of working channels is reduced by one. Then, when one of the working channels fails, it is replaced by the backup and the SFCC remains operable. Self diagnostics and self calibration are performed without interrupting ongoing conversions with the aid of the backup channel, which temporarily replaces one of the working converter channels. This SFCC carries out 14-digit parallel conversion of three pulsed-frequency signals with amplitudes of 0.5–10 V at frequencies of 10 Hz – 32 MHz with a conversion frequency of 250 Hz over a large part of its range (for ƒx ≥ 500 Hz). The structure of this SFCC differs from that in Ref. 1 in the switching configuration for choosing the operating mode (Fig. 1). The switch 5 is made up of four switching circuits 1–4. The outputs of the switch are connected to the inputs of four identical converter channels CC1–CC4. The diagnostic g(t) and calibration k(t) signals can be switched to the input of any of the four converter channels. In the following we assume that the SFCC remains operable if at least three of the four converter channels are operable. When one of the three working channels CC1–CC3 fails, its functions are transferred to the backup channel CC4. For this purpose, the converter input signals s1(t)–s3(t) are fed to the input of switching circuit 4. For example, if the first working converter channel CC1 fails, the signal s1(t) will be directed to the input of the backup channel CC4 which replaces the working channel CC1. But in this case the self diagnosis or self calibration operations will inevitably interrupt the ongoing conversions for several tens of milliseconds [1]. Self di
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