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.