The NMR system was re-programmed. Not by me.
the trigger signal is from the laser beam. there are 2 ways, 1 is from the chopper diode, another is by the power meter. the chopper signal is typical square wave. But the power meter has phase delay and relaxation time.
the field sweep is a amplifier connected to the magnetic coil. the amplifier is APEX-PA05 model. we use it as a Voltage-Controlled-Current-Supply. since the magnetic field is depends on Current and the coil resistance is so small that applying a voltage on it will very sensitive.
the RF Amp control is usual, we connect a voltage output in to the “Trig IN”. but the RF Amp just like turned off. when the control changed back to local, every things work well. so, the problem is on the Remote setting of the RF Amp. we checked the manual and it said that to complete control from remote, we may have to connect it with a computer. Oh….