Thank you for the extra details. This certainly helps us have a better idea of the problems you are trying to solve.
Here are a few ideas:
The best way to know this would most likely be to measure the current used by the servo. More details on that below. A value of ~0 would indicate no servo, a value >0 but within reasonable range would indicate a working servo (different current use at idle, accelerating, holding, etc.) and an excessive amount >0 would indicate a stall (possibly damaging the servo) or a short (servo is already damaged). You can get lots of info from profiling the current of any actuator, including RC servomotors.
Again, that would be best done measuring the current of the servo.
You can send the SSC-32U the “VER” command and check the response to see if it is “alive”. That is what the official Lynxmotion software does for the Lynxmotion AL5D robotic arm kits.
A possible idea here is to connect a temperature measurement device to each of your servomotors. An optimal component would be a temperature sensor that provides an analog voltage output that is [0, 5] V DC. This would allow you to know when the motor is too hot (which is typically what happens before it “burns”).
As mentioned before, the SSC-32/SSC-32U does not have any way of detecting the presence of the RC servomotor since its signal pin is only an digital output pin (actually, it goes through a buffer, too). Therefore the microcontroller on the board has no way of detecting anything. Also, detecting anything for each channel would require 32 extra inputs (impossible on that microcontroller) or extra components such as extra PISO buffers (shift registers).
You can measure it electrically. The simplest (and typical) method is to place a shunt resistor between your power source and load and amplify the voltage difference sensed over this special resistor using an amplification circuit. The output of this circuit is then fed to an analog input.
In your case, you would do the following, assuming you want to measure the current (and presence) of a RC servomotor on channel 7:
]Connect the signal pin between the RC servomotor and channel 7./:m]
]Connect the ground pin between the RC servomotor and channel 7./:m]
]Connect the VCC of the RC servomotor to the Vin+ and the VS1/2 pin of channel 7 to the Vin- of your current sensing circuit./:m]
]Connect the Vout of your current sensing circuit to the analog input channel of your choice (VA/VA/VC/Vd/VE/VF/VG/VH)./:m]
A simple current sensing board you can use would be something like: RB-Spa-901. Please note such a board still needs you to solder a shunt resistor on it, too (to be obtained separately). We strongly recommend to check the documentation for this board first. You can find it on the product page under Useful Links.
Unfortunately, such a change would require additional circuitry for each channel. This would then make the SSC-32U’s price prohibitive for hobbyists and schools, which are the main target market. See the note to above about measuring current.
Sincerely,