# DC Voltage sensing using lv-25P

Discussion in 'The Projects Forum' started by Navaneeth1285, Mar 19, 2015.

1. ### Navaneeth1285 Thread Starter New Member

Mar 19, 2015
8
0
hi,
i tried to sense 80 V dc using lv-25p, i initially tried for voltage value of 10V.but i am not obtaining voltage on the secondary side,
primary side resistance is 10k ohm 10W, and my secondary side resistance in 150 ohm, i designed them to obtain a voltage of 3V on the secondary side.
i tried varying the input but there is no change in the secondary side, also my dso is showing negative value..??

2. ### R!f@@ AAC Fanatic!

Apr 2, 2009
9,616
1,082
Diagram please...we are not psychics.

3. ### Navaneeth1285 Thread Starter New Member

Mar 19, 2015
8
0
i also grounded the secondary side with the +/- 12 V supply

4. ### Alec_t AAC Fanatic!

Sep 17, 2013
7,042
1,458
Wired as shown, the primary current should be 8mA if the sensed voltage is 80V. So far so good.
If I understand the datasheet correctly, the secondary current should therefore be 8*1000/2500 = 3.2mA, resulting in 0.48V across the 150 Ohms. How did you get the 3V figure? If you get 0V, either there's a wiring error or the IC is dead/fake.

Edit: Looking at the datasheet again, although the conversion ratio is stated to be 2500:1000, the nominal primary and secondary currents are 10mA and 25mA respectively, implying a conversion ratio of 1000:2500. Something is inconsistent . But that ratio should give 20mA secondary current and hence 3V across the 150 Ohms, as you said.

Last edited: Mar 19, 2015
5. ### Navaneeth1285 Thread Starter New Member

Mar 19, 2015
8
0
hi,
how can i test the LV25p to find whether iis working or not..?
is there any specific method to do so..?

6. ### R!f@@ AAC Fanatic!

Apr 2, 2009
9,616
1,082
Nope ..you have to build the circuit to test.