7i97T Analog Output Problem

Hello all,

I am in the process of retrofitting a Milltronics BR50 bridge mill.  The drives are Panasonic Sigma SGDB analog servo drives.

I am using a 7i97T for drive control and a 7i84U for additional i/o.

The problem I am having is that the analog outputs on the 7i97T don't seem to be putting out enough voltage when connected to the Panasonic drives. When nothing is connected to the 7i97T, a multimeter on the analog outputs reads the expected +/- 10V when set via HAL. However, with the drives connected, the voltage drops to almost 0.

If I put the multimeter in series with the analog output, set to output 10V, to measure current the voltage drops to a fraction of a volt and the current reading on the meter shows about 80mA. One of the little green LEDs on the 7i97T also dims slightly.

The weird thing is that if I use a 3V coin cell connected to the drive's analog in with the same meter in series, the current only measures at 0.1mA. Also, measuring the impedance/resistance of the drive's analog input shows a resistance of around 37kOhms. This is using the same wires as used by the 7i97T, so I don't think it is a wiring fault. 

I don't think it's a HAL problem since the expected voltages can be output via HAL to the disconnected board, and I don't think it's the drive or wiring since the tiny coil-cell battery works.  I'll attach my work-in-progess HAL/INI files below.

Is it possible that the problem lies in the 7i97T? The problem occurs on all the analog outputs and with all three servo drives.

 

Yup, you were right.

I would've thought that since it is a bipolar signal that getting the two wires swapped would just have the effect reversing the sign of the signal. Guess not.

Anyway, it looks like the outputs still work, so massive kudos to PCW for building the card rugged enough to survive a few mistakes.