ADLINK Technology NuDAQ PCI-9812/10 User Manual

Contents

ADLINK Technology NuDAQ PCI-9812/10 User Manual Manual pdf 20 page image

12 • Signal Connection3.2 Analog Input Impedance SettingThis section describes the characteristics of the different inputs ofthe PCI-9812/10.3.2.1 Analog InputPCI-9812/10 has four analog input channels which are connectedthrough connectors J1 ~ J4. The input impedance and inputamplitude range can be changed through soldering the gapswitches on board (refer to PCI-9812/10’s layout). A solder gapswitch consists of two copper pads, the switch can be turned on bysoldering these two pads together. All the four channels have thesame way to configure their input characteristics, and only channel0 is discussed here. There are 2 solder gap switches, named C0LO(channel 0 low impedance) and C05V (channel 0 5V input), to setupthe input characteristics of channel 0. (Please refer to fig. 2.1 insection 2.3)C0LO C05V Input Impedance Input RangeOpen Open High (~15M Ohm) ±1VOpen Close 1.25K Ohm ± 5VClose Open Low (50 Ohm) ± 1V (default)Close Close Low (50 Ohm) ± 5VCAUTION : When the input channel is configured as a highimpedance input, DO NOT leave the input connectorunconnected, the input connector must be connectedto a low impedance signal source to provide a returnpath for the input bias current (<= 15 μA), otherwisehigh voltage will build up at the input of A/D converter.That could damage the A/D converter.Note : 75 ohm input impedance can be achieved by either :1. Replace R95 by a 75 ohm resistor and close C0LO.2. Place a T-connector with a 75 ohm terminator on J1and open C0LO.