AC Pressure Question

I have a question about the pressur in the AC system. Car is an 89 98. Right now, at idle the pressure holds right around 30ish psi. When I increase the idle the pressure on the low side drops to where the low side pressure switch kicks the compressor off. Is this a normal operating situation? I don't ahve the ability to check the high side pressure right now, just low side.

Thanks,
matt