Can you tell if a wattmeter is not working right?

Yes, you can determine if a wattmeter is not working correctly by checking for discrepancies in the readings compared to expected values. If the wattmeter consistently shows values that are significantly higher or lower than those predicted by calculations or measurements from other reliable devices, it may be malfunctioning. Additionally, inspecting the connections, calibration, and condition of the wattmeter can help identify any potential issues. Regular maintenance and testing against a known standard can also aid in ensuring its accuracy.