HP (Hewlett-Packard) E42 ユーザーズマニュアル

3-41. Two separate inputs are provided on the right side of the panel. The A and B inputs are
identical in specification and identical controls are provided for each input to allow maximum

versatility and accuracy.

3-42. HP-IB PROGRAMMABLE INPUT CONTROLS. In COM A position, the output of the
Channel B attenutor is disconnected. The output of the Channel A attenuator is routed to the A
and B input amplifiers as shown in Figure 3-8. In COM A the Channel B AC-DC, X1, X10, X100
Attenuator relays are disabled. The Channel A AC-DC, X1, X10, X100 Attenuator determine the
coupling for the Channel B amplifier.

3-43. The A and B input amplifiers have independent LEVEL and SLOPE controls regardless

of the mode of operation (SEP or COM A).

3-45. AC-DC SWITCH. The AC-DC switch controls the coupling of the external signal to the

attenuator-amplifier by switching a capacitor in series in the AC position or by direct coupling
in the DC position. The advantage of AC coupling is to provide a DC block for signals with a
DC component. DC has the disadvantage of being unable to pass low frequency signals. A
distinct advantage of having DC coupling cover the full bandwidth (DC-100 MHz) is that
extremely accurate time interval or pulse measurements can be achieved even though pulse
widths or repetition rates vary since the trigger point is independent of the duty cycle of the input
signal.

3-46. ATTENUATOR. The attenuator (ATTEN) connects the input signal directly to the

amplifier (in X1) or through a 10:1 attenuator (X10) or a 100:1 attenuator (X100) to increase the

voltage range by 10 or 100 times to allow measurement of high level signals that would other-
wise be impossible without external attenuation.