Can I Connect my own Tachometer or Strobe to the Tach Input of my vb1000, vb2000 or vb3000?

The information provided is for help with Commtest Instruments products:

• vb instrument

QUESTION

Can I connect my own tachometer or strobe to the tach input of my vb1000, vb2000 or vb3000?

ANSWER

Yes you can; however, your strobe must have a digital output (e.g. TTL or switch) and you must obtain the cable and connectors and wire them up yourself. We do not supply the cables because of the very large variety of connectors fitted on strobes and the differing wiring required. We have used and recommend the Monarch Nova-Strobe DB-Plus 115 seen here at Monarch Instruments.

There are many strobes with a digital/TTL output on the market and many of these could potentially be connected to the instrument, but the Monarch Nova is the only one we have tested. If you want to try to connect a different strobe please see the wiring information below.

The instrument's tachometer input requires a Switchcraft connector, model: TA4F. This can be obtained from many electronics components catalogues, for example:

Allied Electronics

part number 932-1202

Ph:1-800-433- 5700 or (1-817) 595-3500

Alternatively, purchase a tachometer extension cable (64009532) from your local reseller. This will provide you with the TA4F connector and cable; you will only need to replace the connector at the strobe end.

Wiring Information

The pins of the TA4F connector are connected internally to the vb instrument as follows:

1. Tach + Positive tach input to vb instrument (isolated).
2. Ground
3. Tach - Return line from tach input (isolated).
4. Supply From the main vb battery; 6 to 9 V; only on while measuring; limited to 100 mA.

Here is a view of the connector from the outside (your connector is numbered but this numbering is very small).

Ascertaining your Tachometer's Digital Output

Now you need to find out what kind of digital output your tach provides. If you don't know, use the instructions below to test if it uses the TTL option first. If this doesn't work try the Switch option.

TTL output

(strobe drives its output to, say, 5 V. e.g. Monarch strobes)

• Connect the Positive (Output) from the strobe to pin 1 of the Switchcraft connector.
• Connect the Negative (Ground) from the strobe to pin 3 of the Switchcraft connector.
• Leave the other two pins of the Switchcraft connector unconnected.

  Note: You will not do any damage by swapping Positive and Negative, the strobe just won't work.

Switch output

(strobe pulls output down to Ground but does not provide an output voltage)

• Connect Switchcraft connector pin 4 back to Switchcraft connector pin 1.
• Connect the Positive (Output) from the strobe to pin 3 of the Switchcraft connector.
• Connect the Negative (Ground) from the strobe to pin 2 of the Switchcraft connector.

  Note: This is the wiring that should be used if using a simple make/break switch output.

Test if the Tachometer is Working

The exact keys you need to press will vary depending on which version of the instrument firmware you are using. Use one of the bulleted instructions below to take a measurement.

• From the Main Menu select Measure>Tachometer Display then press START/STOP.

OR

• From the Main Menu select Measure>Display Options>Tach Display (to ON), press Enter then START/STOP.

OR

• Select Balancing>Trial readings>Initial Reading and press Enter.

FAQ ID: 11678 Last Reviewed: 27/09/2005