DS1923
Hygrochron Temperature/Humidity Logger
iButton with 8kB Data Log Memory
www.maxim-ic.com
SPECIAL FEATURES
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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
Ò
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
Temperature and Humidity Logging in Food
Preparation and Processing
Transportation of Temperature- and Humidity-
Sensitive Goods, Industrial Production
Warehouse Monitoring
Environmental Studies/Monitoring
PART
DS1923-F5
TEMP RANGE
-20°C to +85°C
PACKAGE
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
5.89
0.51
â
16.25
17.35
APPLICATIONS
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IO
GND
Front Side Brand
â
All dimensions are
shown in millimeters.
A1
ORDERING INFORMATION
000000FBC52B
Hygrochron
TM
â
41
1-Wire
â
1-Wire and iButton are registered trademarks of Dallas Semiconductor.
Hygrochron is a trademark of Dallas Semiconductor.
Back Side Brand
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REV: 110504
DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data log Memory
DS1923 ABSOLUTE MAXIMUM RATINGS
IO Voltage to GND
IO Sink current
Operating Temperature and Humidity Range
Storage Temperature and Humidity Range
-0.3V, +6V
20mA
-20°C to +85°C, 0%RH to 100%RH
(See
Safe Operating Range
Chart)
-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
(V
PUP
= 3.0V to 5.25V, T
A
= -20°C to +85°C)
PARAMETER
IO Pin General Data
1-Wire Pullup
Resistance
Input Capacitance
Input Load Current
High-to-Low Switching
Threshold
Input Low Voltage
Low-to-High Switching
Threshold
Switching Hysteresis
Output Low Voltage
Recovery Time
(Note 1)
Rising-Edge Hold-off
Time
Timeslot Duration
(Note 1)
SYMBOL
R
PUP
C
IO
I
L
V
TL
V
IL
V
TH
V
HY
V
OL
t
REC
CONDITIONS
MIN
TYP
MAX
2.2
100
6
0.4
0.7
0.09
5
2
5
0.6
65
8
9.5
480
690
48
70
15
15
2
1.5
1.5
0.15
60
60
7
7
65
71.5
8
720
720
80
80
60
63.5
7
5
8
1
240
287
24
28
75
75
9
2.0
µs
µs
800
10
3.2
0.3
3.4
N/A
0.4
UNITS
kW
pF
µA
V
V
V
V
V
µs
(Notes 1, 2)
(Note 3)
IO pin at V
PUP
(Notes 4. 5)
(Notes 1, 6)
(Notes 4, 7)
(Note 8)
At 4mA (Note 9)
Standard speed, R
PUP
= 2.2kW
Overdrive speed, R
PUP
= 2.2kW
Overdrive speed, directly prior to
reset pulse; R
PUP
= 2.2kW
(Note 10)
t
REH
Standard speed
t
SLOT
Overdrive speed, V
PUP
> 4.5V
Overdrive speed (Note 11)
IO Pin, 1-Wire Reset, Presence Detect Cycle
Standard speed, V
PUP
> 4.5V
Reset Low Time
Standard speed (Note 11)
t
RSTL
(Note 1)
Overdrive speed, V
PUP
> 4.5V
Overdrive speed (Note 11)
Standard speed, V
PUP
> 4.5V
Presence-Detect High
t
PDH
Standard speed (Note 11)
Time
Overdrive speed (Note 11)
Standard speed, V
PUP
> 4.5V
Presence-Detect Fall
Time
t
FPD
Standard speed
(Note 12)
Overdrive speed
Standard speed, V
PUP
> 4.5V
Standard speed (Note 11)
Presence-Detect Low
t
PDL
Overdrive speed, V
PUP
> 4.5V
Time
(Note 11)
Overdrive speed (Note 11)
Standard speed, V
PUP
> 4.5V
Presence-Detect
Sample Time
t
MSP
Standard speed
(Note 1)
Overdrive speed
µs
µs
µs
µs
µs
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PARAMETER
IO Pin, 1-Wire Write
Write-0 Low Time
(Note 1)
Write-1 Low Time
(Notes 1, 13)
IO Pin, 1-Wire Read
Read Low Time
(Notes 1, 14)
Read Sample Time
(Notes 1, 14)
Real-Time Clock
Accuracy
Frequency Deviation
Temperature Converter
Conversion Time
DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory
SYMBOL
CONDITIONS
MIN
TYP
MAX UNITS
Standard speed
Overdrive speed, V
PUP
> 4.5V
(Note 11)
Overdrive speed (Note 11)
Standard speed
Overdrive speed
Standard speed
Overdrive speed
Standard speed
Overdrive speed
+25°C
D
F
t
CONV
-20°C to +85°C
8-bit mode (Note 15)
16-bit mode (11 bits)
iButton package (Note 16)
(Notes 15, 17, 18, 19)
(Notes 15, 17, 18, 19)
Slow moving air (Note 20)
(Note 21)
(Note 22)
With software correction
(Notes 18, 19, 23, 24, 25)
With software correction (Note 18)
(Notes 26, 27)
(Note 28)
At 50%RH (Note 29)
8
0.64
0
60
6
7.5
5
1
5
1
t
RL
+
d
t
RL
+
d
-3
-300
30
240
130
See Temperature
Accuracy Graphs
See Temperature
Accuracy Graphs
30
12
0.04
±5
<1
0.5
±0.5
<1.0
12
0.04
100
120
12
12
15 -
e
1.95 -
e
15 -
d
1.95 -
d
15
1.95
+3
+60
75
600
µs
t
W0L
t
W1L
µs
t
RL
t
MSR
µs
µs
min./
month
PPM
ms
s
°C
°C
s
bits
%RH
%RH
%RH
%RH
%RH
%RH/y
Thermal Response
t
RESP
Time Constant
Conversion Error
Without Software
DJ
Correction
Conversion Error With
DJ
Software Correction
Humidity Converter (Note 30)
Humidity Response
t
RH
Time Constant
RH Resolution
RH Range
RH Accuracy and
Interchangeability
RH Nonlinearity
RH Hysteresis
RH Repeatability
Long-Term Stability
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
Note 8:
Note 9:
Note 10:
Note 11:
Note 12:
Note 13:
Note 14:
Note 15:
Note 16:
System requirement.
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.
Capacitance on the data pin could be 800pF when V
PUP
is first applied. If a 2.2kW 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.
V
TL
, V
TH
are a function of the internal supply voltage.
Voltage below which, during a falling edge on IO, a logic '0' is detected.
The voltage on IO needs to be less or equal to V
ILMAX
whenever the master drives the line low.
Voltage above which, during a rising edge on IO, a logic '1' is detected.
After V
TH
is crossed during a rising edge on IO, the voltage on IO has to drop by V
HY
to be detected as logic '0'.
The I-V characteristic is linear for voltages less than 1V.
The earliest recognition of a negative edge is possible at t
REH
after V
TH
has been previously reached.
Highlighted numbers are NOT in compliance with the published iButton standards. See comparison table below.
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
.
e
represents the time required for the pullup circuitry to pull the voltage on IO up from V
IL
to V
TH
.
d
represents the time required for the pullup circuitry to pull the voltage on IO up from V
IL
to the input high threshold of the bus
master.
To conserve battery power, use 8-bit temperature logging whenever possible.
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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DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory
Note 17:
Note 18:
Note 19:
For software corrected accuracy, assume correction using calibration coefficients with calibration equations for error
compensation.
Software correction for humidity and temperature is handled automatically using the 1-Wire Viewer Software package available
at: http://www.ibutton.com.
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.
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.
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.
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.
Software corrected accuracy is accomplished using the method detailed in the
Software Correction Algorithm for Temperature
section of this data sheet.
Every DS1923 Device is measured and calibrated in a controlled, NIST-traceable RH environment.
Higher accuracy versions may be available. Contact the factory for details.
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.
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.
Individual RH readings always include a noise component (repeatability). To minimize measurement error, average as many
samples as is reasonable.
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
2
, H
2
SO
4
, CI
2
,HCL, H
2
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
All humidity specifications are determined at +25°C except where specifically indicated.
Note 20:
Note 21:
Note 22:
Note 23:
Note 24:
Note 25:
Note 26:
Note 27:
Note 28:
Note 29:
Note 30:
Parameter
Name
t
SLOT
(incl. t
REC
)
t
RSTL
t
PDH
t
PDL
t
W0L
1)
Standard Values
Standard Speed
Overdrive Speed
Min
Max
Min
Max
61µs
(undef.)
7µs
(undef.)
480µs
(undef.)
48µs
80µs
15µs
60µs
2µs
6µs
60µs
240µs
8µs
24µs
60µs
120µs
6µs
16µs
DS1923 Values
Standard Speed
Overdrive Speed
Min
Max
Min
Max
1)
65µs
(undef.)
9.5µs
(undef.)
690µs
720µs
70µs
80µs
15µs
63.5µs
2µs
7µs
60µs
287µs
7µs
28µs
60µs
120µs
7.5µs
12µs
Intentional change, longer recovery time requirement due to modified 1-Wire front end.
PHYSICAL SPECIFICATION
Size
Weight
Safety
See mechanical drawing
Ca. 5.0 grams
th
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)
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DS1923: Hygrochron Temperature/Humidity Logger iButton with 8kB Data Log Memory
Safe Operating Range
100
Humidity (%RH)
80
60
40
20
0
-40
-20
0
20
40
60
80
Temperature (°C)
Storage Only
Safe Operating Zone
DS1923 Temperature Accuracy
Uncorrected Max Error
SW Corrected Max Error
2.0
1.5
Uncorrected Min Error
SW Corrected Min Error
DS1923: Error (°C)
1.0
0.5
0.0
-0.5
-1.0
-20
-10
0
10
20
30
40
50
60
70
80
Temperature (°C)
NOTE:
The graphs are based on 11-bit data.
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