Weigh Scale Mode

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2.4.1 Parameters

Display units: The units to use when displaying mass. Available units are μg (displayed as ug), mg, g, kg,

ounces (oz), pounds, (lb), and stone (st). See Section 2.1 for details.

Averages: Number of points to use when reading weight. The choices available are 2, 4, 8, 10, 16, 32,

50, 64, 100, and 128. The default is 50.

ADC speed: This parameter selects between the two data rates on the installed ADS device, which are

called high-speed and low-speed. When high-speed mode is selected, FAST is shown; for low-speed

mode, SLOW is shown.

(1)

The actual data rate of the ADS1131 or ADS1231 depends on the frequency of the master clock, f

CLK

. In

fast mode, the data rate is f

CLK

/61440; in slow mode, the data rate is f

CLK

/491520. See the ADS1131 data

sheet or the ADS1231 data sheet for further information.

The default setting is low-speed mode.

Calibration weight: This parameter gives the expected mass of the calibration weight used in the

calibration procedure (Section 2.3). The calibration mass can be given in any of the available units, in

three significant figures. The unit is independent of the display unit.

Each digit in the mass is adjusted separately. The currently-selected digit flashes, and can be adjusted

with the VALUE buttons. The PARM buttons are used to select the digit. The unit is adjusted in the same

manner, and flashes when selected.

When the unit is changed, the value changes to the equivalent mass in the new unit.

Save parameters: This screen allows the settings of the ADS1x31REF to be stored in flash memory. It

functions the same as it does in Analysis mode. When ENT or SEL is pressed on this screen, the

ADS1x31REF saves its settings to flash memory. These settings are loaded from flash memory when the

board is reset or powered on. All operating parameters are saved, including scale calibration settings,

voltage reference, display mode, and units.

Version number: This screen displays the version number of the ADS1x31REF firmware.

(1)

The ADS1x31REF cannot detect the frequency of the ADS1231 master clock, so it cannot display the actual data rate of the ADS1231

device.

ADS1131REF and ADS1231REF SBAU175A–July 2010–Revised August 2011

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Analysis Mode

3 Analysis Mode

In Analysis mode, the ADS1x31REF analyzes code output from the installed ADS device and displays it in

different ways. Table 3 summarizes the numerous display modes available, together with example

displays.

NOTE: The values shown in Table 3 are consistent for a 24-bit device, such as the ADS1231.

However, the ADS1131 is an 18-bit device, so the actual number of codes will be fewer than

the examples shown here.

Table 3. Modes and Example Displays

Hex Code Dec Code Voltage ENOB

Raw 1992E9H +1676001 +499.488M n/a

RMS n/a +5.789 +17.495N +23.18BIT

Peak-to-Peak n/a +31.256 +90.293N +21.92BIT

Averaged n/a +1676001 +499.488M n/a

The ADS1x31REF operates in Analysis mode when the mode switch is set to the ANALYSIS position.

The default Analysis mode is RAW HEX.

To change measurement types, hold down DISP and press MODE. This function cycles through the four

available measurement types. When DISP is released, the newly selected measurement is made. To

change units, press UNIT. This option cycles through the available units for the active measurement type.

This procedure can also be done while DISP is depressed; in that case, the new unit is shown by name

on the display. The measurement modes are described in detail in Section 3.2.

The ADS1131 or ADS1231 itself can be configured directly from this mode, as described in Section 3.1.

3.1 Switch Functions

NEW BLOCK: Pressing this switch resets the collection process for the RMS, peak-to-peak, and

averaged measurements.

UNIT: Cycles between available units. Not all units are available in all modes.

DISP: When this switch is pressed, the display shows the current measurement mode and unit. While

DISP is still pressed, pressing NEW BLOCK / MODE cycles through the available measurement modes.

CHIP: Holding this switch down allows the settings of the installed ADS device to be changed, using the

PARM (NEW BLOCK) and VAL (UNIT) buttons.

Pressing PARM while CHIP is pressed down cycles through the available parameters of gain and data

rate.

The gain setting is displayed as GAIN= followed by the gain setting. The gain setting is for display only,

because the gain is fixed at 64 for the ADS1131 and 128 for the ADS1231.

Data rate is shown on the display as SPD=FAST or SPD=SLOW. See ADC speed in the Parameters section

for further information.

If any of these parameters are changed during a multisample measurement, the measurement is

restarted.

SBAU175A–July 2010–Revised August 2011 ADS1131REF and ADS1231REF

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v =

B 1-

REF

s =

(x )-

i =1

E =

N log s :-

2 N

24 : s 0

Analysis Mode

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3.2 Measurement Modes

Raw: In this measurement, codes are read from the installed ADS device and displayed. No processing or

analysis is done on the sample stream. Data can be displayed as hexadecimal codes, decimal codes, or

volts.

Voltage is calculated according to Equation 3:

Where:

• A is the converter gain (64 for the ADS1131 and 128 for the ADS1231)

• v

REF

is the voltage at the converter reference input

• x is the ADC decimal code

• B is the number of converter bits, 2

for the ADS1131 and 2

for the ADS1231 (3)

REF

is adjustable from Configuration mode. By default, it is 5V.

The voltage display is autoranging. All ranges are shown with six significant figures having three decimal

places. The ranges are given in Table 4.

Table 4. Voltage Display Ranges

VOLTAGE RANGE DISPLAY SUFFIX

Nanovolts < 1μV n

Microvolts < 1mV u

Millivolts < 1V m

Volts ≥ 1V V

RMS noise: In this mode, a number of codes are read from the installed ADS device, and an RMS noise

calculation is performed on them using the standard-deviation formula (given in Equation 4):

(4)

The result can be displayed as decimal codes, volts, or an effective number of bits (ENOB). For decimal

codes, s

is displayed directly. (Hexadecimal is not available because s

may be fractional.) For volts, s

is converted to a voltage as in raw mode.

ENOB: E is calculated using Equation 5:

(5)

Where N is the maximum number of available bits (18 for the ADS1131 and 24 for the ADS1231).

The zero case is needed when a string of equal codes is read. This can happen when the converter is

clipping.

This measurement requires a number of codes to be read before a calculation can be made. Therefore,

during the first run, the display shows the word GOT followed by the number of samples collected. This

event happens when the mode is first entered, when the converter configuration changes, or when NEW

BLOCK is pressed.

The number of codes used in the calculation is selected in Configuration mode; 50 codes are used in

laboratory characterization, so this value is the default.

Peak-to-peak noise: In this mode, a number of codes are collected, and the absolute value of the

difference between the minimum and maximum is calculated. The result can be displayed in decimal or

hexadecimal codes, volts, or noise-free bits (ENOB). Volts are calculated as in raw mode; ENOB is

calculated in the same way as in RMS mode.

ADS1131REF and ADS1231REF SBAU175A–July 2010–Revised August 2011

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Part #	897-43-004-90-000000
Description	CONN RECEPT USB TYPE B PCB
Category	SOCKET
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897-43-004-90-000000

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