If your MPG is rated at 30VDC then you should be OK. But I have never seen a 30VDC MPG. It could be that the power for the MPG is OK for 30VDC, but the output may only be 5VDC. You may need to use opto-relays between the MPG and the 24VDC inputs, I have done this on low speed encoders to shift the voltage level.