BACKGROUND

Relative humidity (RH) within concrete can be measured by performing in-situ testing at different depths within a concrete slab. An RH gradient exists within a slab of concrete that has its outer surface exposed; the RH increases as the depth into the slab increases. When the outer surface of the concrete slab is covered by a material that is close to impermeable, thereby preventing moisture from migrating out of the concrete surface, the RH gradient equalizes to an average RH throughout the slab that is about equal to the RH at 40% depth of an uncovered slab drying from the surface only (resting on a vapor retarder), or equal to the RH at 20% depth of an uncovered slab drying from both top and bottom.

A conventional practice for measuring RH in concrete includes forming a hole into a concrete slab at a certain depth, inserting a liner into the hole that will allow for sealing off the sidewalls of the concrete, placing of a seal at the top of the liner to seal off the internal environment, allowing for the equilibration of the RH of the internal environment, and then inserting a testing instrument into the liner to measure the RH. Most currently available instruments consist of a hole liner into which is inserted a probe that includes the sensor and a plastic enclosure. The probe is allowed to equilibrate, then taken out and moved to the next sleeve for the next measurement.

However, these currently available instruments result in undesirable problems relating to the thermal equilibrium of the sensing device and the concrete. Because RH is temperature dependent, an RH sensing element should be in thermal equilibrium with the environment being measured. With these currently available instruments, the probe portion that is inserted into the hole liner needs to come to thermal equilibrium with the concrete before an accurate measurement can be made. When a person handles the probe before insertion, heat is transferred into the probe, making the probe warmer and making the RH readings less accurate. Also, the ambient air is often times at a different temperature than the concrete environment to be measured, causing heat transfer across the probe. Even 1° F. of temperature change in the sensing element can cause inaccuracies in RH measurement of several percent.

SUMMARY

Disclosed herein are exemplary apparatuses and methods that make measuring humidity or moisture in a subject material, such as a concrete slab, quicker, simpler and more accurate, among other benefits.

In one aspect, an apparatus for measuring humidity, moisture, and/or temperature in a material such as concrete, includes a sensor module and, in some cases, a reader module. The sensor module can be mounted within a sleeve that is embedded in the subject material and the reader module can be inserted into the sleeve to connect with the sensor module in order to take a reading. The sensor module can remain embedded in the material, thus allowing a sensor of the sensor module to remain in thermal equilibrium. The hand-held reader module can be connected to various sensor modules to receive humidity, moisture, and/or temperature readings corresponding to various locations within one or more concrete slabs or other materials. Thus, because each sensor module is already in thermal equilibrium, measurement speed is improved.

The sensor module includes a humidity or moisture sensor electrically connected to a first electrical connector. The reader module includes a second electrical connector that is mateable with the first electrical connector to establish an electrical connection between the sensor module and the reader module. The reader module is electrically connectable to and electrically disconnectable from the sensor module. The second electrical connector is electrically connectable to the first electrical connector regardless of a rotational orientation of the reader module relative to the sensor module. One of the electrical connectors can be a set of spring-loaded connector pins while the other electrical connector can be a set of coplanar, concentric landing pads, such as on a printer circuit board, such that redundant pairs of the pins are arranged to contact the same landing pad when the reader module is connected to the sensor module.

Using separate sensor modules allows each RH reading to be more accurate because heat transfer disruptions at the sensor are minimized. Heat transfer can be minimized due to a combination of various advantageous factors, such as: (1) the sensor module remains within the subject material so that the sensor is at thermal equilibrium with the subject material when the sleeve cover is removed; (2) the use of polymer materials for the sleeve and housings that have low thermal conductivity; (3) the minimized contact area between connector pins of the reader module and landing pads of the sensor module; (4) the rotation non-specific nature of the electrical connection between the reader and sensor modules; and (5) the automatic touch-and-sense feature, which results in a minimized time delay between inserting the reader module and the measurements being taken. Each of these benefits is described in detail below.

However, accuracy issues may arise when a sensor module is kept in a high humidity environment for an extended period of time. A humidity sensor may tend to drift such that a humidity reading becomes less accurate over time in relatively humid conditions.FIG. 12illustrates an example of this sensor drift. As shown atFIG. 12, a relative humidity (RH) reading (labeled “Sensor RH”) may tend to drift apart from a true relative humidity (labeled “Reference RH”) as time progresses, with the error increasing as time goes in. Moreover, the error may be more than a few percent.

To improve the accuracy of sensor readings, methods and systems described herein estimate and correct for sensor drift in high humidity conditions. Accordingly, methods and systems described herein may use memory to store past humidity or other sensor readings so that an estimated amount of sensor drift may be determined to improve the accuracy of sensor readings. A memory may be embedded in each sensor module so that past readings for a given sensor module are stored in the memory of the sensor module. Accordingly, algorithms for sensor drift compensation, and systems and methods that use such algorithms to improve the accuracy of sensor readings, are disclosed herein.

Additionally, the use of past sensor readings to compensate for drift incentivizes the regular taking of and storage of sensor readings. Thus, in some embodiments, sensor modules may be provided with on-board controllers and power sources that enable a sensor module to regularly wake itself, take sensor readings, and store the sensor readings in memory even without connection to an external power source (e.g., without connection to a reader module). Thus, even if sensor readings are not regularly captured using a reader module, a sensor module may obtain a stored history of sensor readings that may be used to compensate for drift correction.

Additionally, in some embodiments, sensor modules may be provided with wireless transceivers that may be used to wirelessly communicate with other sensor modules (e.g., via mesh networks or other types of networks) or other computing devices (e.g., servers, reader modules, and the like), which may enable sensor readings to be automatically collected and analyzed without use of a reader module.

The foregoing and other objects, features, and advantages of the invention will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures.

