# Homework Help: Voltmeter design

1. Dec 26, 2005

### electronic engineer

We were asked to design digital voltage and current meter with 3 ranges
(20 100 200) v for voltages and two ranges
(2, 20)A for amperes
Note: supply voltage is 5V
maximum value for resistors of ampere meter must not exceeded 0.5 ohm

V1=Vin. (R2+R3+R4)/(R1+R2+R3+R4)
V2=Vin.(R3+R4)/(R1+R2+R3+R4)
V3=Vin.(R4)/(R1+R2+R3+R4)

Where V1=V2=V3=V4=1 V
Vin changes respectively with V1,V2,V3 as 20,100,200
So we used those equations mentioned above when we considered R1+R2+R3+R4=6000 Kohm but we get these values:
R4=R3=30Kohm
R2= -30
Note: we have no problem with current meter,that's why I haven't referred to it at the attachment
Need help!

2. Dec 26, 2005

### electronic engineer

attachment

sorry, i can't download the my schematic cause it exceedes the max.file size

i don't know may be try later

3. Dec 26, 2005

### Maxwell

What type of file are you trying to attach?

4. Dec 26, 2005

### electronic engineer

PNG file , but it's oversize (about 400KB)