m=

w

fs

c

-

c

fs

zs

Weigh Scale Mode

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2.1

Display

Weigh scale mode can display mass in these units:

μg (displayed as ug), g, kg, pounds (lb), stone (st),

Internally, mass is measured in grams, and calibration factors are stored in grams. At display time, grams

are converted to the desired display unit using the conversion factors given in Table 1.

xxx

(2)

The avoirdupois units used by the ADS1x31REF are equal in the imperial and U. S. customary systems.

Table 1. Unit Conversion Factors and Display Formats

Unit

Multiplier

Format

micrograms (

μg)

10

6

nnn.nnnug

milligrams (mg)

1000

nnn.nnnmg

grams (g)

1

nnn.nnng

kilograms (kg)

10

–3

nnn.nnnkg

ounces (oz)

0.035274

nnn.nnnoz

pounds (lb)

0.0022046

nnn.nnnlb

stone (st)

157.473

× 10

−6

nnstnn.nn

The display format for stone differs from the format used for the other units. One stone is equal to fourteen

pounds; weight in stone is commonly expressed as a number of stone followed by a number of pounds.

On the ADS1x31REF, two digits are shown for stone, followed by st, followed by pounds displayed to two

decimal places.

2.1.1

Calculation of Mass

Mass is calculated from ADC code using the formula:

w = m

● c + w

where:

•

w = mass

•

c = the ADC code

•

w

•

m, w

m is a calibration constant, and is calculated using Equation 1:

(1)

where w

applied, and c

w

w

(2)

2.2

Button Functions

2.2.1

TARE

The tare function allows the mass of a substance to be measured separately from the mass of its

container. When the TARE button is pressed, the scale measures the mass and records it. This reading is

subtracted from each subsequent measurement.

The recorded tare value can be reset to zero by holding the TARE button down for at least one second.

Tare is also reset following a calibration.

8

ADS1131REF and ADS1231REF

SBAU175A

– July 2010 – Revised August 2011

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