please help, how to control a speedometer

[Arian Ghafouri]

Hi guys, I bought an instrument panel that has tachometer and speedometer

the tachometer works perfectly with the tachometer function in simhub !
i searched the google about how to control a tachometer with an arduino and i found the below code and thats work too :
tone(TachoPin, (RPM * 4) / 120);

but I have issue to how to control the speedometer ?? can anyone help me ?
thanks