The paper

Boxes, speed, gain, and the calibration pulse. Everything else is built on this.

Understand the measurements

How long is one small box?

At 25 mm/s the paper moves 25 mm every second, so each 1 mm box is 1/25 of a second, 40 ms. Doubling the speed to 50 mm/s halves the time per box to 20 ms. Veterinary strips are often run at 50 mm/s to spread out fast rhythms.

Count the small boxes in a large box

Five small boxes make one large box: 5 mm, which is 200 ms at 25 mm/s and 0.5 mV at 10 mm/mV.

Measure the calibration pulse

The machine prints a 1 mV pulse so you can check the gain. At the standard 10 mm/mV it stands exactly 10 mm, two large boxes, tall. If it does not, every amplitude on the strip is off by the same factor.

Mark one second

One second is 25 mm at 25 mm/s: five large boxes. The small tick marks along the top of the paper are printed every 3 seconds.