Microphone and Sensors

Sensor Update Feb 2017

For best results we now recommend the use of the Peterson Vibration pick-up.

It is a piezo-acoustic contact sensor, with clip mount and requires no additional adapters to connect to the iPhone! It provides the best vibration pick-up and is not affected by room noise.

> Peterson PitchGrabber on Amazon <

Note that similar products such as Peterson TP-3 do not work with iPhone.

Mic/Sensor Calibration

Place the iPhone's internal microphone, or an external sensor, as close to the clocks escapement as possible or where it is the loudest. This will vary with each type of clock. Ideally it would be inside the case or even attached to the movement plates. The closer the better for accurate hearing of the tick and for better isolation from ambient noise disturbing the readings.

Some ideas on sensor placement

Slide the Sensitivity Level Bar so that each tick of the clock lights a box and advances it to the next square. One box for each tick. Care should be taken so that no ticks are missed, but also that its not so sensitive that extra sounds are heard. You should also aim for a steady BPM (beats per minute) readout as well. This small step of accurate calibration will greatly aid in the overall accuracy of the measurements. Experiment with locations for the best results.

Putting The Clock In Beat

You will not be able to achieve perfect zero due to the inherent errors of the clocks escapement teeth. Adjust as close as possible. For example, on a mantel clock you can level the clock by raising one side or the other of the clock by small amounts and listen for even ticks. Watch the Δ for finer adjustment. If the clock is on the wall, then move the bottom of the case left or right by a small amount and listen for evenness in the ticks. Again use the Δ for finer adjustment. For gross adjustments, the pendulum crutch needs to be adjusted. This should only be attempted by a qualified clockmaker.

Clock Time Regulation

It is imperative to mention that the longer your test sample is, the more stable and more accurate the Error Rate will be. A test of at least ten minutes or more should be conducted for a Rate of any value. 30 minutes or more will allow for more complete analyzation of the data should you wish to go more in depth for troubleshooting purposes.

After a stable Error Rate has been determined, the weight on the pendulum needs to be raised or lowered by turned the nut or screw holding it onto the pendulum. Small amounts are all that are necessary. Half a turn is a good starting point for a minute of error. This of course will vary greatly depending on the type of clock and length of the pendulum. Let the pendulum settle its swing before retesting. Some mantel or bracket clocks are adjusted from the front of the dial with a key. This adjusts the length of the pendulum and has the same effect. Again small adjustments.

Data File Saving & Use

The raw data measured time between ticks is saved in a .txt file. These times are measured to the 15th decimal place. An example of the data file is below:

These times can then simply be imported to your favourite spreadsheet for further use. For example, the times can then be charted or used to figure the BPM for each tick, or the running error average at each tick and then charted. Each chart would then have its own information to give. A specific pattern can be found, an instability figured or a bad tooth on a wheel can be found.

60 BPM Single Pallet Tooth Eccentricity

60 BPM 10 Minute Error Rate Chart

60 BPM 30 Minute Error Rate Chart

Should the need arise, a full range of conservation and restoration services of your antique clock can be provided by: www.antiqueclockrestore.com

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