How to connect Digital Outputs

Digital Outputs need a load to reach their full "speed"

At first connection to a high resistance input like an oscilloscope, Gantner Instruments Digital Outputs will seem slow and unresponsive.

This happens because the output needs a load to help pull the voltage down.

With the right load you can reach frequencies of up to 10kHz.

As specified in the datasheet of the Q.bloxx XL D101 module:

Load capacity >0.5 A >0.1 A <0.1 A
response time 10µs 100µs 1000µs


The outputs are specified for 30VDC / 0.5 A, so the response time is at its fastest right at the upper end of the load capacity.

Wiring diagram from the datasheet:

How to connect an additional resistance if the used Digital Input has a very high resistance:

The resulting resistance determines how fast the Digital Output can react. Please keep in mind, that at 30V and 0.5A a power of 15 W will be in parts converted to heat. All the power through a pull down resistor is converted to heat, so the resistor needs to be able to withstand the thermal load.