Serial RS-232: (see here for USB)

There are two types of serial leads, ones for laboratory instruments and ones for field instruments. Only three connections are used, RX, TX and Gnd.  The table below shows the connections, 25 pin connections are shown for historical reference only:
 

Computer		Instrument
9 pin female	Older 25 pin female	Field 9 pin male	Lab 9 pin female	Older 25 pin male
2	3	2	3	2
3	2	3	2	3
5	7	5	5	7

Laboratory instruments tend to use a 9 pin female to 9 pin female moulded cable with pins 2 and 3 'twisted'. Field instruments come with a 9 pin male to 9 pin female lead, either a ribbon cable with IDC connectors or a custom made lead (if the portable PC was available to ACM Instruments during manufacture). 

If there is a problem with the serial cable, please contact ACM Instruments for a replacement.