SU864550A2 - Device for measuring distribution function of random errors of analogue-digital converters - Google Patents

Description

Such a device makes it possible to measure the error distribution function of the ADC in the presence of variation with a smaller error.

Figure 1 shows the functional diagram of the device; 2, diagrams showing his work.

The device contains the source 1 of the reference voltage, connected through the node 2 of the addition of voltages to the input of the controlled ADC 3, the output of which is connected to the input of the element 4 of the comparison of codes, and the second input of the latter is connected to the terminal of the reference code. The direct output of the code comparison element 4 is connected to the input of the switch 5, the outputs of which are connected to the corresponding inputs of memory block 6, and to the subtractive input of the reversible counter 7. The inverse output of the code comparison element 4 is connected to the summed-up input of the reversible counter 1, the output of which is sequentially through the adder 8 and the code-voltage converter 9 are connected to the second input of the voltage addition unit 2. In addition, the device contains a controlled oscillator 10, the output of which is connected to the inlet of the controlled ADC 3 and to the counting input of the second reversible counter 11, the overflow output of which is connected to the inputs of the counting block 12 and the trigger 13. The output of the second reversible counter 11 is connected to the second the input of the adder 8 and the control input of the switch 5, and the output of the counting unit 12 is connected to the input of the Stop of the controlled generator 10. The direct and inverse outputs of the trigger 13 are respectively connected to the summed and subtractive inputs and a down counter 11.

The device works as follows.

From the output of the source 1 of the reference voltage, through the node 2, the addition of voltages to the input of the controlled ADC 3 is supplied with a voltage corresponding to the nominal value of the boundary between the Nth and N + 1th quanta. On the Start signal, the controlled oscillator 10 starts operating, which triggers the A / D converter 3. By virtue of the presence of random error, codes appear on the EHV of the A / D converter 3, corresponding to Mth or N + 1th quanta. Element 4 of the code comparison compares the code arriving from the DCT with the reference code N + 1, and outputs at its direct output a signal of a logical unit in the event of a coincidence of the codes and a logic zero signal - otherwise.

Next, the signal from the output of the code comparison element 4 simultaneously goes to the switch 5, where it is used to build the distribution function and to the input of the reversible counter 7,

where used to determine current values of the expectation. If the average voltage at the output of the ADC 3, equal to the nominal value of the boundary between the Nth and N + 1th quanta, does not correspond to the actual value of the boundary, then the probability of occurrence of the N-oro codes and N + 1th quanta are not equal between themselves which causes the predominance of counting signals either on the summing or subtracting inputs of the reversing counter 7. In the counter, either positive codes or negative codes accumulate, the higher bits of which, through the adder 8, control the operation of the 9-code-voltage. Voltage from the output of converter 9 code - voltage is summed up by node 2 by adding voltages to the source signal 1 of exemplary voltage so that the probability of occurrence of N-oro and N + 1 codes becomes the same.

At the same time, each pulse from the output of the controlled generator 10 is fed to the counting input of the reversible counter 11. Since the initial trigger 13 is in one state, the pulses are summed in the reversible counter 11. Its code is summed up with the code of the reversible counter 7, and the sum A voltage code is input to the transducer 9. A voltage equal to the sum of the current value of the expectation and the step sweep voltage is supplied from the output of the converter 9. The voltage at the input of the ADC 3 is equal to the sum of the voltage from the output of the source of exemplary voltage 1, the voltage equal to the current value of the estimate of the mathematical expectation of the instrumental error and the step voltage of the analysis levels (Fig.2). After the overflow counter overflows at the time t, the trigger 13 changes its state and the pulses in the counter 11 are subtracted, i.e. sweep voltage decreases. The required number of such cycles is determined by the capacity of the counting unit 12.

Thus, the analysis levels defined symmetrically with respect to the mathematical expectation of the instrumental error in each cycle, increase, tick and decrease, this allows to take into account the appearance of hysteresis when porting the function of the instrumental error.

Claims (1)

1. USSR author's certificate 683015, cl. H 03 K 13/02, 1976 (prototype).