Measuring the synchronous response time of a safety light curtain (including both cascaded and non-cascaded types) requires specialized equipment to capture the time difference between "obstruction occurrence" and "protection signal output." The key is to accurately record the interval between these two critical time points. The following is the specific measurement method, required equipment, and precautions:
I. Core Measurement Principle
The essence of synchronous response time is the time difference between the "trigger signal" and the "response signal":
Trigger signal: The moment the optical axis is obstructed (or when an electrical signal simulating obstruction is input);
Response signal: The moment the safety light curtain outputs a protection signal (such as when a relay opens or the safety output signal toggles).
The time interval between these two signals, recorded using high-precision instruments, is the synchronous response time.
II. Required Equipment
High-precision oscilloscope
Bandwidth ≥ 100MHz, sampling rate ≥ 1GS/s (to ensure capture of microsecond or even nanosecond signal changes);
At least two channels (one for the trigger signal and one for the response signal). Trigger Signal Source
Actual Occlusion Method: A light shield with a photoelectric sensor (when blocking the optical axis, the sensor synchronously outputs an electrical signal to the oscilloscope, marking the "trigger moment");
Electrical Signal Simulation Method: A signal generator (outputs an electrical signal compatible with the grating's receiving end, simulating an "occlusion" trigger; suitable for laboratory calibration).
Test Fixture
A bracket to secure the grating (ensures optical axis alignment and prevents shaking that affects occlusion stability);
An occlusion drive (such as a pneumatic actuator or high-speed motor, controls the light shield to block the optical axis at a stable speed, reducing operator error).
Auxiliary Tools
Coaxial cable (reduces signal transmission delay);
Insulated test leads (connect to the grating output terminals to prevent short circuits);
Electromagnetic shielding box (optional, reduces the impact of ambient electromagnetic interference on the measurement).
III. Specific Measurement Steps
1. Basic Setup (applicable to both non-cascaded and cascaded gratings)
Install the safety grating according to the manual (align the transmitter and receiver, and ensure the distance is within the rated protection range). Connect the power supply and load (such as a safety relay or PLC). Ensure the light barrier is operating properly: when unobstructed, it outputs a "safety signal" (e.g., relay closed, PNP high level); when obstructed, it outputs a "protection signal" (e.g., relay open, PNP low level).
2. Measuring Non-Cascaded Safety Light Barriers
Signal Connections:
Oscilloscope Channel 1: Connect the "trigger signal source" (e.g., the output of a photoelectric sensor on the light barrier, which generates a pulse when obstructed);
Oscilloscope Channel 2: Connect the light barrier's "protection signal output" (e.g., the normally open contact of a safety relay, which closes and generates a voltage level change when protected).
Trigger Measurement:
Use the driver to control the light barrier to quickly block any optical axis of the light barrier (the blocking time must be greater than the light barrier's response time to avoid false positives).
The oscilloscope automatically records the time difference between the rising edge of the channel 1 pulse (blocking start) and the level change edge of channel 2 (protection signal output). This is the synchronous response time.
Repeat Verification: Repeat the measurement 3-5 times with different optical axes and blocking speeds, and take the average value to reduce random errors. 3. Measuring Cascaded Safety Light Barriers (Pay Special Attention to "System Synchronicity")
Cascaded systems require measuring the time from "any unit is blocked" to "the entire system outputs a protection signal." The steps are as follows:
Multi-node monitoring:
Connect an oscilloscope channel to the output of the master controller and the signal terminals of at least two slave units in the cascade system (e.g., channel 2 measures the master controller output, channel 3 measures slave unit 1, and channel 4 measures slave unit 2).
Aim the trigger signal source at the optical axis of one of the slave units.
Verifying Synchronicity:
Block the optical axis of the target slave unit and record the time it takes the master controller to output the protection signal (the difference between the time and the trigger signal).
Also, observe whether the signals of other slave units are synchronized with the master controller (the time difference should be ≤ 1ms, depending on the product standard) to avoid partial non-response due to cascade delay.
Full-range testing: Block the optical axes of different slave units and repeat the measurement to ensure consistent response times across the entire system.