The DCP-2 has a universal input power supply unit which accepts either 110 or 230V ac mains power at 50/60Hz. In addition, the DCP-2 may be operated from an external 12V dc power source, e.g. a vehicle battery. The 12V dc input connector is disconnected by a relay when ac power is present, so cannot be used as a power source. The DCP-2 is protected against reverse battery connection by a zener clamp and a self-reset fuse.
The DCP-2 provides a low-noise negative constant-current power supply to drive the downhole amplifiers. The 96V compliance voltage allows a maximum wireline resistance (conductor 7) of at least 500 ohms.
The DHA (downhole amplifier) module requires negative current for operation. Positive current is blocked by a diode and may therefore be used to operate an optional Gamma section, which may be located either above or below the geophones.
The DCP-2 provides input protected, high impedance, ac coupled, differential buffers for each channel. The buffers effectively add 6dB of gain. Assuming the standard DHA gain of 54dB, the total system gain is therefore increased to 60dB (x1000). Nominal maximum output voltage is 20 volts peak to peak.
Mute circuits: The DCP-2 has output mute circuits to reduce the amplitude of power switching transients. Also, channels 4-6 remain muted in single tool mode.
Motion monitor and alarm: The DCP-2 provides a responsive 6-channel monitor display as that tool motion can be observed during run-in. The display is sensitive enough to be used as a background noise monitor. The DCP-2 also provides a (lack of) motion alarm which monitors the vertical component of the lowest tool and sounds a warning if the tool appears to have hung up.
The winch and line 7 connectors remain as for the DCP-2 and Geochain GPP. Early DCP-2 units have a D25 type signal interface connector and require the AS968 cable. Later units incorporate a 1.5m captive cable, terminated with a GSP compatible 14-19P plug.
Tool connector: The tool connector SK1 (the circular 9-pole 20-21S socket) may be connected directly to an analogue ASR or ESR tool via our AS961 test cable. A cable simulator is not required. For connection via a wireline, use cable AS959.
Signal output connector: The 14-19P signal output connector may be connected to any of our DAQ, ASP or GSP recording system. The six differential output signals are able to drive a full-scale swing of +/- 20V into a 10 kΩ load. Early DCP2 units have a demountable signal output cable; later units are fitted with a more reliable captive signal output cable.
AUX7 connector: The AUX7 connector (Lemo 1BS), may be used to connect the auxiliary equipment (typically a Gamma tool surface panel) to wireline conductor 7. Note that access to wireline conductor 7 is via the “Grab7” relay, located on the backplane PCB.