Kippzonen UVS-E-T UV Radiometers Bedienungsanleitung PDF herunterladen (Seite 10)

The formula for R

max

is:

max

= ([VT+] - 6 V) / 1.2 A

where [VT+] is the supply voltage and R

max

is the sum

of the total wire resistance and the internal resistance

of the power supply.

Example 1:

The supply voltage is 12 VDC. The internal resistance

of the power supply is 1 Ω (i.e. voltage drop of 1 V at 1

A load). Then the allowable total wire resistance (sum

of positive and negative supply wire) is 4 Ω.

Example 2:

To calculate the minimum voltage that is required for

correct operation of the radiometer with the standard

cable of 10 m length, the above equation has to be

reformulated as follows:

[VT+] = 1.2A • R

tot

+ 6V

where R

tot

is the sum of the resistances (internal

resistance of the power supply and total wire

resistance). With the wire resistance of 0.15Ω/m a total

wire resistance of 2 x 1.5Ω = 3Ω for the standard 10 m

cable is obtained. With an internal resistance of 1Ω

(power supply) the sum of the resistances is 4Ω

(equals R

tot

). To compensate for the voltage drop over

the wires and power supply, the voltage supply [VT+]

must be at least 10.8V. Hence, with a power supply

(internal resistance 1Ω) that provides at least 10.8V the

radiometer will operate correctly.

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Kippzonen UVS-E-T UV Radiometers Bedienungsanleitung Seite 10