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Hi

Same question as here: https://community.teltonika-networks.com/2331/rut955-analog-input-voltage-range-extension-%26-scaling?show=2331#q2331

Need to scale analog input voltage input.

I have hardware revision 1714 and need to know the resistance on analog input.

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I measured the input impedance for DIN 1, You find it here: https://community.teltonika-networks.com/26636/input-impedance-rut955

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Hello,

RUT955 Analog input voltage divider uses R1 = 100 kOhm and R2 = 14.7 kOhm value resistors.

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Thank you, but I that does not answer the question.

R1 and R2 are the resistors I will have to connect to reduce my voltage due to the 24V maximum value on the RUT955 input. Ideally I will want to reduce my voltage by 50%.

What I need is the internal resistance of the RUT955 input port that is in parallel with the R2 resistor.
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Hello,

The resistors R1 and R2 values I gave is router internal analog input circuit resistance. Check this picture:

Change external 100K resistor value to reduce your input voltage, since with given values maximum input voltage is 48V

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Can You give me the internal impedance value for DIN 1 too (latest hardware revision)? Thank You!
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Hello,

May I ask why this information is required for you?

Since to activate RUT955 DIN1, it must be shorted to ground.

BR,

Tomas
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I'll connect it to an open collector. And for the purpose of saving power, the current shall be as low as possible, as well into the base of my output, as well as through the collector from DIN1. To make sure to drop well below 1.2 V, i need the input resistance. Also, if someone has long leads between the switch and the input, it can be interesting.

I measured it myself in the meantime:

https://community.teltonika-networks.com/26636/input-impedance-rut955

9.2 kΩ is actually not very high, so it's not that easy to pull it down, You need <7.2 kΩ or >160 µA to ground to come below 1.2 V. This info is missing in the documentation.

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I have check with RnD and they have confirmed that internal impedance is ~9 kΩ. Tolerable external resistance is up to ~5kΩ.