A dipstick is one of several devices dipped into a liquid to perform a chemical test or to provide a measure of quantity of the liquid.
A testing dipstick is usually made of paper or cardboard and is impregnated with reagents that indicate some feature of the liquid by changing colour. Medical dipsticks can be used to test for a variety of liquids for the presence of a given substance, known as an analyte. For example, urine samples might be tested for haemoglobin, nitrite (produced by bacteria in a urinary tract infection), protein, glucose and occasionally urobilinogen or ketones.
They are usually brightly-coloured, and extremely rough to touch.
Dipsticks can also be used to measure the quantity of liquid in an otherwise inaccessible space, by inserting and removing the stick and then checking the extent of it covered by the liquid. The most familiar example is the dipstick in an internal combustion engine, which is a metal strip or thin flexible coil used to measure the quantity of fuel or lubricating oil. Generally the procedure for reading the dipstick is to remove it, clean it with a rag or paper towel to provide a fresh surface for the liquid to contact, then reinsert it. The stick is then removed once more and the level is compared to markings on the dipstick which indicate the required level. A car's transmission fluid sometimes has a similar though usually shorter device.
A dipstick can also be used to check the amount of beer remaining in an ale cask. The stick (generally stainless steel or brass) is made of thin square rod or flat strip, and is inserted through the small hole in the shive on the top of a horizontal cask. If double-decker racking is used a flexible strip may be useful, since casks on the lower rack might not have enough headroom for a rigid rod to be inserted. Because of the round shape of a cask, the intervals between marks vary along the length of the stick:
|Gallons||mm from bottom end|