Oscilloscope Gated Counter, Totalizer Mode

With a suitable sensor or detector, events that needs to be counted can be converted to electronic pulses. The oscilloscope counter can count these pulses. The counter operates independently of the oscilloscope acquisition system, so it can count whether the oscilloscope is in Run or has Stopped. By using a gate, it is possible to precisely control the start and duration of the counting period and count for specific amount of time. From this, other quantities such as flow rate and concentration can be determined.

Using a gated counter is helpful when a system is already operating and the quantity to be counted is already accumulating.

Oscilloscope Setup

Channels 1 and 2 are a paired as input source and gate source. Similarly, Channels 3 and 4 are a paired. Choose any oscilloscope channel as the input for the signal to be counted (I chose Ch 3). The paired channel is used as the gate source.

Press Trigger Setup and make the Trigger source channel the same as input source. Set the trigger parameters according to the input signal.

From the Analysis menu choose Counter

The counter window appears in the upper left corner of the screen, but can be dragged to any convenient location.

On the Counter menu choose Mode: Totalizer, Source: (pulse source input channel), Rising or falling pulse edges, and Level (voltage level setting for pulse detection) 

Then select Gate Setting and turn Gate On to display Gate parameters:

The gate Type may be specified by a voltage level with positive or negative polarity or the gate may be specified by a rising or falling pulse edge.

Use the universal knob (Intensity/Adjust) or Input Pad to set the detection Level for the gate.

Gate Setup

The gate may be any convenient voltage source. Using a function generator allows you to produce a very precise time interval over which to count. The gate may be, for example, a logic high pulse with a start time determined by a trigger and a stop time determined by the duration of the gate pulse. 

Below channel 2 of our SDG1032X Plus arbitrary waveform generator is configured to produce a 3Vdc gate for 60 seconds after pressing Trigger.

To demonstrate use of the gate-controlled counter, Ch1 of the AWG is used as the input source and is set up to output 1uS pulses continuously at 1 kHz. It is a good idea to test the gate with a source that known output (such as this 1 kHz signal) and verify the correct count over the gate time interval.

If counting correctly, 60,000 pulses should be counted on the oscilloscope at the end of 60 seconds

The image below shows the continuous source signal (C3) and the gate signal (C4). The totalizer has stopped counting at 60,000. If C4 receives another valid gate input, the totalizer will continue counting from 60,000. The count value can be zeroed at any time by choosing Totalizer Reset from the Counter menu.