Ultrasonic or Microwave?

[whatoncewas]

Shock sensors seem to be common on the cheapo DIY install alarms. Some also come with others.

What's better, ultrasonic sensor or microwave? And why can't I find a cheapo one with both (along with the standard shock type?).

Cheers,

 

[Firewarrior]

usually alarms dont come with both microwave and ultrasonics. They mainly do the same thing except microwaves are more popular with convertiable cars.
Ultrasonics work on the base of a grid, if the grid is broken the alarm goes off.
Microwaves work on the base of a bubble.
Micrwave can have both interior and exterior protection (in the sense of dual zone)
I have heard that having both can cause interferance but i havent encountered any and i am using both
Also some cheapo alarms have the shock sensor built into the siren, i.e. if the siren moves the alarm goes off, these are the kind you will find if u have a loud exhaust and drive by and it sets it off.

 

[arseofbox]

Ultrasonics work on the base of a grid, if the grid is broken the alarm goes off.
Microwaves work on the base of a bubble.

What? Thats rubbish, where have you heard that?

An Ultrasonic sensor has an effective radius and range (like a microphone or your eye) outside of which, it cannot hear anything (Thats why a car has 2 sensors). A ultrasonic sensor is a microphone, attached to an amp / filter that is tuned to respond to frequencies higher than human hearing (glass breaking has a frequency spectrum like that). Thats why theyre not popular in convertibles.

Microwave systems use (I presume) a system of emitting and recieving microwaves (or waves around that wavelength), and look for major differences in the recieved waveform to tell if theres an intruder.

To be clear about it, both sensing types use a 3D field pattern and monitor for certain differences in the signal coming from that field.

Micrwave can have both interior and exterior protection (in the sense of dual zone)

Yes. that is the advantage of it, and about that much is technically true in Sam's post.

 

[whatoncewas]

Right, thanks Tom.

So which would be better for my Uno? Should I use both anyway?

 

[arseofbox]

Right, thanks Tom.

So which would be better for my Uno? Should I use both anyway?

If microwave's available, go for that.

Ultrasonic's are only really used to sense glass breakage, but microwaves will sense movement in the area they cover.

 

[whatoncewas]

Excellent, ok, thanks.