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General => Technical support => Topic started by: benb2000 on May 06, 2004, 10:03:47 AM

Title: Effective Input Impedance of the A/D Inputs
Post by: benb2000 on May 06, 2004, 10:03:47 AM
What is the effective DC input impedance of the Analog Inputs on the T100MD-888+?.

Some of the literature indicates a 2k resistor in series with the inputs, and the forum has indicated a 0.1uf cap across the input to ground on channels 1 to 6; channels 7 and 8 donot have the cap.

What would be the effective output impedance of Channels 7 and 8 if used as Analog outputs? Do these channels have the 2k resistor in series as well?

Your assistance is appreciated
Title: Re:Effective Input Impedance of the A/D Inputs
Post by: support on May 07, 2004, 09:21:38 AM
The effective impedance on the ADC/DAC pin on MD888 and MD2424 are > 1 M ohms.

Yes, all new T100MD888+ and  T100MD2424+ there are already 2.2K resistor in series with all the AD1 to AD8 and AD1 to AD6 has 0.1uF capacitor in parallel to filter out high frequency noise on the analog inputs. AD7 (DA1) and AD8(DA2) do not have the 0.1uF capacitor.
Title: Re:Effective Input Impedance of the A/D Inputs
Post by: benb2000 on May 07, 2004, 09:34:09 AM
Thankyou.

 Then I would expect at least a 2k output impedance on the DAC of Cchannels 7 and 8.
Title: Re:Effective Input Impedance of the A/D Inputs
Post by: support on May 11, 2004, 09:00:26 AM
Output impedance on the DAC 1 & 2 are much greater than 2.2K. So usually the DAC only provide a reference voltage and does not have ability to drive any load. It has to be connected to high impedance analog input of other devices.