SU1670670A1 - Device for measuring time of contacting of camera synchronous contact - Google Patents

Abstract

This invention relates to optical instrumentation, namely, devices for testing photographic equipment. The purpose of the invention is to improve the measurement accuracy of the contact time of the sync contact by reducing the methodological measurement error. A device for measuring the duration of contacting a camera contains a resistor, an exemplary frequency generator, a coincidence circuit, an inverter, a one-shot, a counter, a register, a digital scoreboard, a one-shot, a register, an inverter and a resistor. When the device is operated, by recording the measurement result in the register, the influence of the contact preder is eliminated, as a result, the measurement accuracy is improved. 2 Il.

Description

The invention relates to the field of optical instrumentation, namely, devices for testing photographic equipment.

The aim of the invention is to improve the accuracy of measuring the duration of contact by using the digital method of counting the time interval from the moment of closure until the sync contact is fully closed, including the moments of its opening due to bounce.

Figure 1 shows the block diagram of the proposed device; Fig. 2 shows timing diagrams explaining the operation of its component parts (a is the conductivity of the sync contact, b is the voltage at the output of the single vibrator, c is the voltage at the output of the coincidence circuit, g is the number of pulses corresponding to the digital code at the output of the register) .

Device for measuring the duration of contact of a sync contact

contains a device 1 reset input, a sync contact 2, a resistor 3, an inverter 4, a one-shot 5, an exemplary frequency generator 6, a matching circuit 7, a counter 8, a register 9, and a digital display 10. The resistor 3 is connected to the power terminal of the inverter 4 and the first the output of the tested sync switch 2, the second output of which is connected to the common wire; the output of the inverter 4 is connected to the input of the single-vibrator 5 and the input to record information in the register 9; the output of the one-shot 5 is connected to the first input of the coincidence circuit 7, the second input of which is connected to the output of the generator 6 of the reference frequency; the output of the coincidence circuit is connected to the input of the counter 8, n - whose output bits are connected to the n-input bits of the register 9, the outputs of which are connected to the digital display 10; the reset input of the device 1 is connected to the installation inputs of the counter 8 and register 9.

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ABOUT

The device works as follows.

To set the device to its original state, before starting the tests from the output 1 of resetting the device to the same inputs of the counter 8 and the register 9, a signal is applied that sets the zero voltage level at their outputs.

A reset signal must be generated by an external sensor (not shown) before the timing of the timing contact. At the output of inverter 4 there is a low logic level, as the input of the inverter is connected via a resistor 3 to the power supply. The first closure of the tested sync contact 2 at the output of the inverter 4 a high logic level signal appears, the leading edge of which triggers a single vibrator 5, the output of which produces a high logic level pulse whose duration determines the contact duration measurement interval and significantly exceeds the tolerance limit for the contact duration controlled sync contact (Fig. 26). This impulse is fed to one input of the coincidence circuit 7, to the other its input impulses are received from the generator 6 of exemplary frequency. At the output of the coincidence circuit 7, a packet of pulses of an exemplary frequency of duration T is formed and (Fig. 2c) the counter 8 starts counting pulses arriving at its input from the output of the coincidence circuit 7. When the sync-contact 2 is opened, the output of the inverter 4 is a low-level signal, on the falling edge of which the output state of the counter 8 is recorded into the register 9 (Fig. 2d). The recording in register 9 occurs during the interval of measurement of Ti at the moment of each opening of the tested sync contact 2 (Fig. 2d). As a result, at the time of the end of the interval Ti, the outputs of the register 9 will have a digital code proportional to the time interval from the moment of the first closure of the sync contact 2 until it is fully opened, i.e. the duration of the contact Tk. The measurement result is displayed on the digital display 10.

The maximum value of the absolute discreteness error is ± 1 of the lowest digit of the count, and this value does not depend on the value of the measured value Tk and is determined by the sampling unit. To decrease the sampling error, it is necessary to increase the pulse frequency of the sample pulses.

If the follow-up period of the generator generator pulses is T0br, the frequency of the following is Robr, then during the contact time Tk, m pulses will pass

ten

t t p -Tk RoBR and, therefore, the measured time T

15

Tk Ch Tobr or Tk

m

Robr

Measurements are indirect. In order to obtain a direct indication in a device with a rigid logic (without a microprocessor), the pulse frequency must be chosen so that where K

1,2,3 then Tk tons

For example, when choosing Rob. 10 kHz (Tobr. 0.01 ms) absolute error

will be ± 0.01 ms, which will provide a measurement of the contact time of the sync contact of the camera 1 ms with a relative error of ± 1%, excluding the methodological measurement error arising from the bounce of the sync contact.

Claims (1)

Apparatus of the Invention A device for measuring the duration of contact of a sync contact a camera comprising an exemplary frequency generator associated with a coincidence circuit, the output of which is connected to a counter, a sync contact and a digital display, characterized in that improving the accuracy of measuring the duration of contact of a sync contact, a register, an inverter, a one-shot and a resistor are entered into the device, and through a power source the resistor is connected to the input the inverter and the first output of the sync contact, the second output of which is connected to the common wire, and the output of the inverter is connected to the one-shot input and the write input to the register, the one-shot output is connected to the auxiliary input of the coincidence circuit, the n-output bits of the counter are connected the register, the outputs of which are connected to the digital display, and the device reset input connected to the installation inputs of the counter and register.