Figure 3 

NOTE: The Figure shows '2# Bypass Volt Detect Fail-Set' fault, where 2# refers to module 2 and 0# to the bypass module. 

Q3: When the UPS reports ‘Bypass Volt Detect Fail-Set’ fault, what are the typical troubleshooting steps? 
A: When the sampling resistor circuit is faulty, the typical troubleshooting steps are as follows: 
1. Check the actual input/output values of the circuit based on the location of the fault; 
2. If the actual input/output values are normal, consider whether the detection circuit on the PCB board is faulty; (For modular UPS systems, first determine if the power module/bypass module detection circuit is faulty)

Q4: How to detect whether the sampling resistor circuit on the PCB board is faulty? 
A: The method for detecting a sampling resistor circuit fault is as follows: 
1. Locate the corresponding point on the PCB board; use the ohmmeter function (Ω) of a multimeter; touch the two points on the PCB board by the multimeter probes; check whether the resistance value is within the effective range (the deviations of resistance value will vary depending on the type of resistor) ; (The detection points are shown in Figure 4).

Figure 4