DS1923 Maxim, DS1923 Datasheet - Page 11

• Manufacturer Part Number: DS1923
• 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
• Manufacturer: Maxim

The DS1923 is an ideal device to monitor for extended
periods of time the temperature and humidity of any
object it is attached to or shipped with, such as fresh
produce, medical drugs and supplies, and for use in
refrigerators and freezers, as well as for logging climat-
ic data during the transport of sensitive objects and
critical processes such as curing. A 1.27mm diameter
hole in the lid of the device allows for air to reach the
humidity sensor. The rest of the electronics inside the
DS1923 is sealed so that it is not exposed to ambient
humidity. Note that the initial sealing level of the
DS1923 achieves the equivalent of IP56. Aging and use
conditions can degrade the integrity of the seal over
time, so for applications with significant exposure to liq-
uids, sprays, or other similar environments, it is recom-
mended to place the Hygrochron™ under a shield to
protect it (refer to Application Note 4126: Understanding
the IP (Ingress Protection) Ratings of iButton Data
Loggers and Capsule ). The hydrophobic filter may not
protect the DS1923 from destruction in the event of full
submersion in liquid. Software for setup and data
retrieval through the 1-Wire interface is available for free
download from the iButton website (www.ibutton.com).
Hygrochron is a trademark of Maxim Integrated Products, Inc.
Hygrochron Temperature/Humidity Logger
______________________________________________________________________________________
Detailed Description
-1.0
-2.0
-3.0
-4.0
-5.0
2.0
1.0
0.0
iButton with 8KB Data-Log Memory
-20
-10
0
10
TEMPERATURE ( C)
20
30
This software also includes drivers for the serial and USB
port of a PC and routines to access the general-purpose
memory for storing application-specific or equipment-
specific data files.
All iButton data loggers are calibrated/validated against
NIST traceable reference devices. Maxim offers a web
application to generate validation certificates for the
DS1922L, DS1922T, DS1922E, and DS1923 (tempera-
ture portion only) data loggers. Input is the iButton’s
ROM code (or list of codes) and the output is a valida-
tion certificate in PDF format. For more information,
refer to Application Note 4629: iButton
Calibration and NIST Certificate FAQs .
The block diagram in Figure 1 shows the relationships
between the major control and memory sections of the
DS1923. The device has six main data components:
64-bit lasered ROM; 256-bit scratchpad; 512-byte gen-
eral-purpose SRAM; two 256-bit register pages of time-
keeping, control, status, and counter registers and
passwords; 64 bytes of calibration memory; and 8192
bytes of data-logging memory. Except for the ROM
and the scratchpad, all other memory is arranged in a
single linear address space. The data-logging memo-
ry, counter registers, and several other registers are
40
50
60
RTC Accuracy (Typical)
70
80
®
Data-Logger
Overview
11