In general it is difficult to say because acquisition performance varies greatly according to factors such as communication speed and PC specifications, in addition to the number of connected units and channels. In your case, the speed of your serial communication will have a big effect. If you connect an RS-232/422 converter to your PC's RS-232C port and perform communications at 9600 bps, you could expect around 30 channels per unit on 4 units. For instance, if you wish to connect five or more units of the µR1000/µR1800 and maintain acquisition at one-second intervals, use multiple PC COM ports and place every four units on a separate RS-422 connection.