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REV:

110504

DS1923

Hygrochron Temperature/Humidity Logger

iButton with 8kB Data Log Memory

www.maxim-ic.com

SPECIAL FEATURES

§ Digital Hygrometer Measures Humidity with 8-Bit

(0.6%RH) or 12-Bit (0.04%RH) Resolution

§ Operating Range: -20 to +85°C; 0 to 100%RH

(see Safe Operating Range)

§ Automatically Wakes Up, Measures Temperature

and/or Humidity and Stores Values in 8kB of
Datalog Memory in 8- or 16-Bit Format

§ Digital Thermometer Measures Temperature with

8-Bit (0.5°C) or 11-Bit (0.0625°C) Resolution

§ Temperature Accuracy Better than ±0.5°C from

-10°C to +65°C with Software Correction

§ Built-in Humidity Sensor for Simultaneous

Temperature and Humidity Logging

§ Capacitive Polymer Humidity-Sensing Element

§ Hydrophobic Filter Protects Sensor Against Dust,

Dirt, Water, and Contaminants

§ Sampling Rate from 1s up to 273hrs

§ Programmable Recording Start Delay After

Elapsed Time or Upon a Temperature Alarm Trip
Point

§ Programmable High and Low Trip Points for

Temperature and Humidity Alarms

§ Quick Access to Alarmed Devices Through

1-Wire

Conditional Search Function

§ 512 Bytes of General-Purpose Memory Plus 64

Bytes of Calibration Memory

§ Two-Level Password Protection of All Memory

and Configuration Registers

§ Communicates to Host with a Single Digital Signal

at Up to 15.4kbps at Standard Speed or Up to
125kbps in Overdrive Mode Using 1-Wire Protocol

§ Individually Calibrated in a NIST-Traceable

Chamber

§ Calibration Coefficients for Temperature and

Humidity Factory Programmed into Nonvolatile
(NV) Memory

APPLICATIONS

§ Temperature and Humidity Logging in Food

Preparation and Processing

§ Transportation of Temperature- and Humidity-

Sensitive Goods, Industrial Production

§ Warehouse Monitoring

§ Environmental Studies/Monitoring

ORDERING INFORMATION

PART TEMP

RANGE

PACKAGE

DS1923-F5

-20°C to +85°C

F5 iButton

iButton DESCRIPTION

The DS1923 temperature/humidity logger iButton is a
rugged, self-sufficient system that measures
temperature and/or humidity and records the result in
a protected memory section. The recording is done at
a user-defined rate. A total of 8192 8-bit readings or
4096 16-bit readings taken at equidistant intervals
ranging from 1s to 273hrs can be stored. In addition to
this, there are 512 bytes of SRAM for storing
application-specific information and 64 bytes for
calibration data. A mission to collect data can be
programmed to begin immediately, or after a user-
defined delay or after a temperature alarm. Access to
the memory and control functions can be password-
protected. The DS1923 is configured and
communicates with a host-computing device through
the serial 1-Wire protocol, which requires only a single
data lead and a ground return. Every DS1923 is
factory-lasered with a guaranteed unique 64-bit
registration number that allows for absolute
traceability. The durable stainless-steel package is
highly resistant to environmental hazards such as dirt,
moisture, and shock. Accessories permit the DS1923
to be mounted on almost any object, including
containers, pallets and bags.

F5 MICROCAN

GND

0.51

5.89

16.25

17.35

Front Side Brand

000000FBC52B

1-Wire

Hygrochron

Back Side Brand

All dimensions are
shown in millimeters.

1-Wire and iButton are registered trademarks of Dallas Semiconductor.
Hygrochron is a trademark of Dallas Semiconductor.

DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data log Memory

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DS1923 ABSOLUTE MAXIMUM RATINGS

IO Voltage to GND

-0.3V, +6V

IO Sink current

20mA

Operating Temperature and Humidity Range

-20°C to +85°C, 0%RH to 100%RH
(See Safe Operating Range Chart)

Storage Temperature and Humidity Range

-40°C to +85°C, 0%RH to 100%RH
(See Safe Operating Range Chart)

This is a stress rating only and functional operation of the device at these or any other conditions above those
indicated in the operation sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods of time may affect reliability.

DS1923 ELECTRICAL CHARACTERISTICS

PUP

= 3.0V to 5.25V, T

= -20°C to +85°C)

PARAMETER SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

IO Pin General Data

1-Wire Pullup
Resistance

PUP

(Notes 1, 2)

2.2

Input Capacitance

(Note

100 800 pF

Input Load Current

IO pin at V

PUP

µA

High-to-Low Switching
Threshold

(Notes 4. 5)

0.4

3.2

Input Low Voltage

(Notes 1, 6)

0.3

Low-to-High Switching
Threshold

(Notes 4, 7)

0.7

3.4

Switching Hysteresis

(Note 8)

0.09

N/A

Output Low Voltage

At 4mA (Note 9)

0.4

Standard speed, R

PUP

= 2.2k

Overdrive speed, R

PUP

= 2.2k

Recovery Time
(Note 1)

REC

Overdrive speed, directly prior to
reset pulse; R

PUP

= 2.2k

µs

Rising-Edge Hold-off
Time

REH

(Note 10)

0.6

2.0

µs

Standard speed

Overdrive speed, V

PUP

> 4.5V

Timeslot Duration
(Note 1)

SLOT

Overdrive speed (Note 11)

9.5

µs

IO Pin, 1-Wire Reset, Presence Detect Cycle

Standard speed, V

PUP

> 4.5V

480

720

Standard speed (Note 11)

690

720

Overdrive speed, V

PUP

> 4.5V

Reset Low Time
(Note 1)

RSTL

Overdrive speed (Note 11)

µs

Standard speed, V

PUP

> 4.5V

Standard speed (Note 11)

63.5

Presence-Detect High
Time

PDH

Overdrive speed (Note 11)

µs

Standard speed, V

PUP

> 4.5V

1.5

Standard speed

1.5

Presence-Detect Fall
Time
(Note 12)

FPD

Overdrive speed

0.15

µs

Standard speed, V

PUP

> 4.5V

240

Standard speed (Note 11)

287

Overdrive speed, V

PUP

> 4.5V

(Note 11)

Presence-Detect Low
Time

PDL

Overdrive speed (Note 11)

µs

Standard speed, V

PUP

> 4.5V

Standard speed

71.5

Presence-Detect
Sample Time
(Note 1)

MSP

Overdrive speed

µs

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PARAMETER SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

IO Pin, 1-Wire Write

Standard speed

120

Overdrive speed, V

PUP

> 4.5V

(Note 11)

6 12

Write-0 Low Time
(Note 1)

W0L

Overdrive speed (Note 11)

7.5

µs

Standard speed

15 -

Write-1 Low Time
(Notes 1, 13)

W1L

Overdrive speed

1.95 -

µs

IO Pin, 1-Wire Read

Standard speed

15 -

Read Low Time
(Notes 1, 14)

Overdrive speed

1.95 -

µs

Standard speed

Read Sample Time
(Notes 1, 14)

MSR

Overdrive speed

1.95

µs

Real-Time Clock

Accuracy

+25°C -3

min./

month

Frequency Deviation

-20°C to +85°C

-300 +60

PPM

Temperature Converter

8-bit mode (Note 15)

Conversion Time

CONV

16-bit mode (11 bits)

240

600

Thermal Response
Time Constant

RESP

iButton package (Note 16)

130

Conversion Error
Without Software
Correction

(Notes 15, 17, 18, 19)

See Temperature

Accuracy Graphs

°C

Conversion Error With
Software Correction

(Notes 15, 17, 18, 19)

See Temperature

Accuracy Graphs

°C

Humidity Converter (Note 30)

Humidity Response
Time Constant

Slow moving air (Note 20)

(Note

21)

8 12 12 bits

RH Resolution

0.64

0.04

%RH

RH Range

(Note 22)

100

%RH

RH Accuracy and
Interchangeability

With software correction
(Notes 18, 19, 23, 24, 25)

±5

%RH

RH Nonlinearity

With software correction (Note 18)

RH Hysteresis

(Notes 26, 27)

0.5

%RH

RH Repeatability

(Note 28)

±0.5

%RH

Long-Term Stability

At 50%RH (Note 29)

<1.0

%RH/y

Note 1:

System requirement.

Note 2:

Maximum allowable pullup resistance is a function of the number of 1-Wire devices in the system and 1-Wire recovery times. The
specified value here applies to systems with only one device and with the minimum 1-Wire recovery times. For more heavily
loaded systems, an active pullup such as that found in the DS2480B may be required.

Note 3:

Capacitance on the data pin could be 800pF when V

PUP

is first applied. If a 2.2k

W resistor is used to pull up the data line 2.5µs

after V

PUP

has been applied, the parasite capacitance does not affect normal communications.

Note 4:

, V

are a function of the internal supply voltage.

Note 5:

Voltage below which, during a falling edge on IO, a logic '0' is detected.

Note 6:

The voltage on IO needs to be less or equal to V

ILMAX

whenever the master drives the line low.

Note 7:

Voltage above which, during a rising edge on IO, a logic '1' is detected.

Note 8:

After V

is crossed during a rising edge on IO, the voltage on IO has to drop by V

to be detected as logic '0'.

Note 9:

The I-V characteristic is linear for voltages less than 1V.

Note 10:

The earliest recognition of a negative edge is possible at t

REH

after V

has been previously reached.

Note 11:

Highlighted numbers are NOT in compliance with the published iButton standards. See comparison table below.

Note 12:

Interval during the negative edge on IO at the beginning of a presence detect pulse between the time at which the voltage is 90%
of V

PUP

and the time at which the voltage is 10% of V

PUP

Note 13:

e represents the time required for the pullup circuitry to pull the voltage on IO up from V

to V

Note 14:

d represents the time required for the pullup circuitry to pull the voltage on IO up from V

to the input high threshold of the bus

master.

Note 15:

To conserve battery power, use 8-bit temperature logging whenever possible.

Note 16:

This number was derived from a test conducted by Cemagref in Antony, France, in July of 2000.

http://www.cemagref.fr/English/index.htm

Test Report No. E42.

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Note 17:

For software corrected accuracy, assume correction using calibration coefficients with calibration equations for error
compensation.

Note 18:

Software correction for humidity and temperature is handled automatically using the 1-Wire Viewer Software package available
at: http://www.ibutton.com.

Note 19:

WARNING: Not for use as the sole method of measuring or tracking temperature and/or humidity in products and articles that
could affect the health or safety of persons, plants, animals, or other living organisms, including but not limited to foods,
beverages, pharmaceuticals, medications, blood and blood products, organs, flammable, and combustible products. User shall
assure that redundant (or other primary) methods of testing and determining the handling methods, quality, and fitness of the
articles and products should be implemented. Temperature and/or humidity tracking with this product, where the health or safety
of the aforementioned persons or things could be adversely affected, is only recommended when supplemental or redundant
information sources are used. Data logger products are 100% tested and calibrated at time of manufacture by Dallas
Semiconductor/Maxim to ensure that they meet all data sheet parameters, including temperature accuracy. User shall be
responsible for proper use and storage of this product. As with any sensor-based product, user shall also be responsible for
occasionally rechecking the temperature accuracy of the product to ensure it is still operating properly.

Note 20:

Response time is determined by measuring the 1/e point as the device transitions from 40 to 90%RH or 90 to 40%RH, whichever
is slower. Test was performed at 5L/min airflow.

Note 21:

All DS1923 humidity measurements are 12-bit readings. Missioning determines 8-bit or 16-bit data logging. Battery lifetime is the
same no matter what RH resolution is logged.

Note 22:

Reliability studies have shown that the device survives a minimum of 1000 cycles of condensation and drying, but this product is
not guaranteed for extended use in condensing environments.

Note 23:

Software corrected accuracy is accomplished using the method detailed in the Software Correction Algorithm for Temperature
section of this data sheet.

Note 24:

Every DS1923 Device is measured and calibrated in a controlled, NIST-traceable RH environment.

Note 25:

Higher accuracy versions may be available. Contact the factory for details.

Note 26:

If this device is exposed to a high humidity environment (>70%RH), and then exposed to a lower RH environment, the device will
read high for a period of time. The device will typically read within +0.5%RH at 20%RH, 30 minutes after being exposed to
continuous 80%RH for 30 minutes.

Note 27:

All capacitive RH sensors can change their reading depending upon how long they have spent at high (>70%RH) or low RH
(<20%RH). This effect is called saturation drift and can be compensated through software, as described in the Software
Saturation Drift Compensation section of this data sheet.

Note 28:

Individual RH readings always include a noise component (repeatability). To minimize measurement error, average as many
samples as is reasonable.

Note 29:

Like all relative humidity sensors, when exposed to contaminants and/or conditions toward the limits of the safe operating range,
accuracy degradation can result (see Safe Operating Range chart). For maximum long-term stability, the sensor should not be
exposed or subjected to organic solvents, corrosive agents (strong acids, SO

, H

, CI

,HCL, H

S, etc.) and strong bases

(compounds with PH greater than 7). Dust settling on the filter surface does not affect the sensor performance except to possibly
decrease the speed of response.
For more information on the RH sensor's tolerance to chemicals visit:

http://content.honeywell.com/sensing/prodinfo/humiditymoisture/technical/c15_144.pdf

Note 30:

All humidity specifications are determined at +25°C except where specifically indicated.

Standard Values

DS1923 Values

Parameter

Standard Speed

Overdrive Speed

Standard Speed

Overdrive Speed

Name

Min Max Min Max Min Max Min Max

SLOT

(incl. t

REC

)

61µs

(undef.) 7µs

(undef.) 65µs

(undef.)

9.5µs

(undef.)

RSTL

480µs (undef.)

48µs 80µs 690µs

720µs

70µs

80µs

PDH

15µs 60µs 2µs 6µs 15µs 63.5µs

2µs

7µs

PDL

60µs 240µs 8µs 24µs 60µs 287µs

7µs

28µs

W0L

60µs 120µs 6µs 16µs 60µs 120µs 7.5µs

12µs

Intentional change, longer recovery time requirement due to modified 1-Wire front end.

PHYSICAL SPECIFICATION

Size

See mechanical drawing

Weight

Ca. 5.0 grams

Safety

Meets UL#913 (4

Edit.); Intrinsically Safe Apparatus,

approval under Entity Concept for use in Class I,
Division 1, Group A, B, C, and D Locations (application
pending)

Part Number DS1923