Enabling the Input Each input port has a relay that is used to enable and disable the input. This Ports relay is controlled by the command:

INPut[<port >][:STATe] <mode >

Setting the Input Impedance

The <mode > settings are:

ON - the input is enabled.

OFF - the input is disabled. For the single ended input, the port is set to a high impedance.

At power-on or following a reset, each input port is enabled (<mode > is ON). However, the port used for the measurement is specified by the (@<input port >) parameter of CONFigure/MEASure, or by [SENSe[<chan >]]:FUNCtion.

The impedance of the single-ended input port can be set to 50Ω or 75Ω. The impedance is set with the command:

INPut[<port >]:IMPedance <impedance >

Enabling the 10 MHz Input Filter

The <impedance > settings are:

50 - sets single ended input impedance to 50Ω 75 - sets single ended input impedance to 75Ω

At power-on or following a reset, the impedance is set to 50Ω. The impedance of the differential input ports is 1 MΩ and is not programmable.

The Inverting and Non-inverting Differential Input Ports

The non-inverting (HI) and inverting (LO) differential input ports can be used singly (the non-used port should be grounded), or together such that the difference (algebraic sum) of two signals is supplied to the digitizer. If a single input is applied to the inverting (LO) port, the reading is inverted.

Each digitizer channel has a 10 MHz, 2-pole bessel filter that can be switched into the signal path of the single-ended or differential input. The filter is enabled/disabled with the command:

INPut[<port >]:FILTer[:LPASs][:STATe] <mode >

108 Understanding the HP E1429 Digitizer

Chapter 3

Page 108
Image 108
HP E1429A manual Setting the Input Impedance, Enabling the 10 MHz Input Filter