Ask the experts

Using single-ended accelerometers with the 2777A differential charge amplifier


We are replacing our differential accelerometers with 7703A's that have single-ended outputs. We are also using 2777A differential charge amplifiers. Can I use the 2777A with the 7703A, or do I have to replace the charge amplifiers?


Yes. You can make the differential input into a single-ended input by connecting Pin B, of the input plug to the shell of the connector. Pin A is connected to the center conductor pin of the accelerometer's 10-32 connector. The accelerometer should be isolated using an isolation stud to prevent ground loops. When using a single-ended accelerometer, the amplifier's gain and frequency response is the same as a differential accelerometer.

Differential accelerometers offer the ultimate in common mode noise rejection. Using the above approach makes the 2777A into a single-ended amplifier therefore it does not provide for rejection of common mode signals. This may not pose a limitation if operated in an area where common-mode noise sources (radio transmitters or other electromagnetic producing devices) are not present.

The cable should be Meggitt's low-noise cable type 3090C or 3090DV.

Note: When using the 2777A Differential Remote Charge Converter's DRCC "verify" voltage input will have one designated input at ground potential, due to one of the accelerometer inputs grounded as a single ended mode (coaxial). The 2777A input connector will have the center conductor from the 7703A accelerometer as either pin A (+) or B (-) and the other tied to the shell/gnd. Usually the center conductor is connected to pin A (as described above) since it is the non-inverting input (see below diagram).