ShatterPoint 5620 sensor shock sensitivity

Has anyone used 5600 series glassbreak sensors from Sentrol/GE?
They are supposed to have both an acoustic glassbreak detector and a shock detector for frame mounting.
I got one of these sensors off e-bay (unused) and the shock sensitivity seems very poor. When I have it mounted with screws to a wooden frame and follow the shock testing procedure in the manual, it only responds with 2 long LED flashes when I whack the frame within a few inches of the sensor, not any further that that.

The shock sensor is a little piezo sounder, which seems fine. There is no sensitivity adjustment, in fact, there is not even any amplification before the signal from the piezo goes into a PIC microprocessor. So, I am not sure what could be wrong with it. Is it just a bad sensor or do they all have low shock sensitivity?

 

The specs for these things is tuned for false alarm resistance; I think the acoustic break sensor is the primary sensor, and the impact sensor is the backup.

 

It requires both shock and acoustic signal to alarm. From the installation instructions on testing:
"Using the 5709C hand-held tester (set for proper glass type), hold tester at furthest point of
glass and press test button while simultaneously rapping lightly on the glass with the handle of a screwdriver."

The whole point of having dual technologies is that the sensitivity of each can be higher, without false alarms.

 

I looked into the circuit of the 5620, it uses a piezo buzzer as a shock sensor wired directly to the comparator inputs of the microprocessor. It requires 5-10 mV of signal to trigger it. So I got an op-amp amplifier circuit on E-bay for $1 shipped from China. With a gain of 100 for the piezo sensor it works pretty well now.

The false alarm immunity is quite good. One can bang on the window, or play window break sounds and nothing happens. But when the two happen together, it triggers reliably. So the idea of the sensor is good, just the implementation is poor, they tried to save a buck!