DS1825(3)

NAME
DS1825 - Programmable Resolution 1-Wire Digital Thermometer with ID

MAX31826
    - Digital Temperature Sensor with 1Kb Lockable EEPROM

MAX31850 MAX31851
    - Cold-Junction Compensated Thermocouple

SYNOPSIS

  Thermometer with hardware address pins (DS1825)

3B [.]XXXXXXXXXXXX[XX][/[ | latesttemp | power | prog_addr | temphigh | templow | tempres | ]]

  Digital Temperature Sensor with 1Kb Lockable EEPROM (MAX31826)

3B [.]XXXXXXXXXXXX[XX][/[ temperature | latesttemp | power | memory | pages/page.[0-15|ALL] | prog_addr | ]]

  Cold-Junction Compensated Thermocouple (MAX31850 and MAX31851)

3B [.]XXXXXXXXXXXX[XX][/[ temperature | latesttemp | thermocouple | fault | open_circuit | ground_short | vdd_short | power | prog_addr | ]]

FAMILY CODE

3B

SPECIAL PROPERTIES

  power
read-only,yes-no
Is the chip powered externally (=1) or from the parasitically from the data bus (=0)?

  prog_addr
read-only, 0-15
A distiguishing feature of the DS1825 (3) is the ability to set hardware pins for an address (0-15). This is an alternative to the unique 64-bit address that is set in the factory.

  temperature
read-only, floating point
Measured temperature with 12 bit resolution.

For the MAX31850 MAX 31851 this is the cold-junction temperature -- the temperature at the chip. See thermocouple

  temperature9 temperature10 temperature11 temperature12
read-only, floating point ( DS1825 only)

Measured temperature at 9 to 12 bit resolution. There is a tradeoff of time versus accuracy in the temperature measurement.

The MAX31826 MAX31850 MAX31851 measure all temperatures at 12 bit resoltion and will return that resolution to all the possible temperature properties.

  latesttemp
read-only, floating point
Measured temperature at 9 to 12 bit resolution, depending on the resolution of the latest conversion on this chip. Reading this node will never trigger a temperature conversion. Intended for use in conjunction with /simultaneous/temperature.

  fasttemp
read-only, floating point
Equivalent to temperature9

  thermocouple
read-only, floating point ( MAX31850 MAX31851 only)

Measured temperature of the thermocouple at 16bit resolution. Cold-junction temperature compensated.

The actual thermocouple type used is set by the selected chip type, and is not discoverable in software.

The MAX31826 does NOT have temperature thresholds and temperature alarm.

MEMORY
Only the MAX31826 supports memory functions.

  pages/page.0 .. pages/page.15 pages/page.ALL
read/write, binary
EEPROM memory pages of 8 bytes each. See the datasheet about locking contents.

  memory
read/write, binary
EEPROM memory of 128 bytes. See the datasheet about locking contents.

FAULT REPORTING
Only the MAX31850 MAX31851 supports fault reporting.

  fault
read-only, yes-no
Fault in last thermocouple conversion

  open_circuit
read-only, yes-no
Thermocouple leads disconnected.

  ground_short
read-only, yes-no
Thermocouple lead shorted to ground.

  vdd_short
read-only, yes-no
Thermocouple lead shorted to supply voltage.

STANDARD PROPERTIES

DESCRIPTION

  DS1825
The DS1825 (3) is one of several available 1-wire temperature sensors. Alternatives are the DS18S20 (3), DS18B20 (3), and DS1822 (3) as well as temperature/voltage measurements in the DS2436 (3) and DS2438 (3). For truly versatile temperature measurements, see the protean DS1921 (3) Thermachron (3).

The DS1825 (3) can select between 4 resolutionsspanning the fastest/roughest and slowest/best.

  MAX31826
The MAX31826 shares a family code with the DS1825 but has differences in some of its functions.

The MAX31826 has 128 btes of EEPROM memory (as 16 pages of 8 bytes) while the DS1825 has no memory available.

The MAX31826 measures temperature at 12 bit resolution as fast as the DS1825's lowest resolution (and always uses 12-bit resolution). On the other hand it has no temperature thresholds or alarm function.

ADDRESSING

Both the MAX31826 and the DS1825 allow hardware selection of part of the address, which can assist selecting between chips is some circuit designs.

DATASHEET

DS1825
    http://pdfserv.maxim-ic.com/en/ds/DS1825.pdf

MAX31826
    http://datasheets.maxim-ic.com/en/ds/MAX31826.pdf

SEE ALSO

AVAILABILITY
http://www.owfs.org

AUTHOR
Paul Alfille (paul.alfille@gmail.com)