Probe options

There are two basic types of probe: sensors and actuators. Sensors measure an environmental condition and report the current reading to the monitor. The monitor is then able to decide whether the sensor is in an alarm state.

If an alarm state is entered then one or more actions can be performed by the monitor. The monitor can perform regular alarm functions like send an email and it can instigate an action using an actuator probe.

Actuator probes perform some kind of action in the real world. For instance, a sensor controlled relay can switch on the power to a device, or a dry contact probe can trigger an alarm in a fire alarm system.

Some probes, like dry contact probes, can be both a sensor and an actuator.

It can be confusing to figure out which probes are required when purchasing an environmental monitoring system. A summary is presented at the end of this section to help you decide which environment monitors support the probes you wish to use.

Temperature

Temperature is by far the #1 concern for I.T. people when monitoring their data centre environment.

Why is the temperature so important when computer manufacturers advertise wide operating temperature ranges in their technical specifications?

The temperature range specified for our main Dell server[1] is 10° to 35°C (50° to 95°F). Given the wide operating temperature range, why can’t we run our server at a sizzling 34.9°C?

Data centre temperature is of critical importance to the lifetime and reliability of electrical equipment. High temperatures reduce the lifetime and reliability of electrical equipment. So, we could run our server at 34.9°C but we should expect reduced reliability as a consequence.

Combined temperature & relative humidity

Relative humidity is unlikely to be a major headache in more temperate climes, it is good to keep an eye on it to make sure that your air conditioning system is keeping the air humidity within reasonable bounds.

High humidity can cause a problem because under some conditions the water vapour in the air can condense on the electrical components inside your data centre. Water and electronics don’t mix too well.

Low humidity can cause just as many problems as high humidity. Low humidity can cause static electricity to build up in electrical equipment. Static build up can damage electrical components.

Wetness

Water and I.T. equipment don’t mix well.

Wetness probes are most commonly deployed underneath the air conditioning system or underneath the raised floor area.

Wetness probes are available in two types.

The first type, as shown in the image above, uses a conductive rope. When the rope is wet it conducts an electric current more easily and so a measure 1 to 100 can be made denoting the level of wetness. The main downside to using the rope type of wetness probe is that when the rope gets wet it can take awhile to dry out. Use in dirty environments can also inhibit the accurate operation of the wetness probe.

The second type of wetness probe is a single point probe where water is measured in a single location. The black box in the image above has an inlet where water is measured. Instead of a level of wetness, the probe above is a simple wet or dry probe.

The single point wetness probe is best when combined with a plastic tray to catch all of the water dropped into it and concentrate it into a single point. The probe would then be placed at the point where the water concentrates. This type of wetness probe is typically used beneath your air conditioning unit where the area to be covered is limited.

The rope based wetness monitor is best used where a large area needs to be monitored like underneath a raised floor for instance. It wouldn’t be ideal to place a large tray underneath a typical raised floor because of the large area to be covered.

Security

A security probe is able to detect the break of an electrical circuit held together by two weak magnets. A security probe is commonly used to alarm on the opening of a door, usually a cabinet door when it is expected that the door will remain closed. Security probes are often paired up with a camera. The opening of a server cabinet door often triggers a camera to take a photo of the unauthorised person. The image can then be emailed or recorded for later examination.

Power presence

Most data centres have, at the very least, a backup power supply provided by a UPS. Larger data centres typically also have a fully redundant power supply backed by an off grid electricity generator.

UPS battery life is typically only an hour or two so your servers will be powered for a short time usually long enough that they can be shut down safely.

In addition, the air conditioning system typically won’t be supplied with power when the primary power fails due to their massive electricity drain. Consequently, the heat level in the data centre is going rise quite quickly.

That’s where the power detector probe comes into its own. You can alarm when your primary power source fails giving you time to take action before the secondary power starts to fail.

The power presence alarm only detects the presence or absence of power. If you need to monitor the quality and/or quantity of the electricity, a power monitor probe is required.

Power monitor

In these more energy conscious times knowing how much power your equipment is consuming is increasingly important. You can’t know that you’ve reduced power consumption unless you can measure it.

In addition, you can measure the quality of the power delivered by your energy supplier. Many types of equipment are very sensitive about the electricity feed into them.

Smoke detector

Personally I’m not convinced exactly where a smoke detector probe fits into a data centre manager’s tool bag given that, in the United Kingdom and probably the rest of Europe, there are tight fire regulations in data centres.

Data centres have to be fire proof to at least one hour with regularly tested fire alarms and, in many cases, automatic fire suppression systems too.

Given that, I’m not sure exactly where a smoke detector probe fits in. Perhaps, if your facilities people can’t be relied upon to let you know of an incident then a smoke detector provides a relatively cheap way to remain in the loop.

Motion detector

A motion detector probe is usually combined with a camera to provide a security solution.

The probe uses passive infrared to detect movement so it can be used in low light conditions.

When movement is detected the system will alarm permitting you to specify one or more actions to be performed. The most common action is to take a picture using a camera and then email the image to an interested party.

Sensor Controlled Relay

The relay probe controls a single power supply. It is able to switch the power on or off or to cycle the power to a device.

The relay probe is generally used as a method to control a single device as part of an alarm action. Typically a probe will enter an alarm state, like a temperature probe exceeds a given threshold, and an alarm is triggered. The environment monitor will then switch on an appropriate piece of equipment.

Dry contact

Dry contacts have been standard for many years in the alarm industry. More recently Uninterruptible Power Supply (UPS) and air conditioner manufacturers have used the dry contact to indicate alarm conditions. The dry contact is a binary indicator, it can only be in an on or off condition. In order to provide information on a number of alarm conditions a manufacturer will provide more than one dry contact port.

Dry contact probes can detect an alarm condition in a device and/or they can indicate an alarm to a device.

In the case of the AKCP products the dry contact probe can be used to detect an alarm condition or to indicate an alarm condition to a device.

The Sensatronics environment monitors can detect an alarm condition but not trigger an alarm.

Air flow

Data centres rely on a constant stream of cold air being introduced into a data centre and hot air being removed.

The air flow probe allows you to measure the speed of air flowing over the probe giving you a good indication as to how well the air conditioner is performing. Though the probe only indicates the speed of air flow. It will not tell you what the temperature of the air is. In order to measure both the air flow and the temperature you will require a temperature probe in addition to the air flow probe.

Camera

With the addition of a camera your environment monitor can become a convenient, integrated security solution for your data centre when combined with security and movement probes.

Siren & strobe

The siren & strobe sensor provides a visual and/or audible alert, ideal for situations where it is imperative that an alarm is acted upon immediately. Plainly, a siren & strobe is best used in a staffed environment.

A common situation is for a sensorProbe or securityProbe to monitor the temperature in a server room. When the temperature rises above an acceptable level the Siren and/or strobe light is activated in a manned Network Operation Centre (NOC) or other permanently manned area. The personnel can then undertake whatever action is needed to mitigate the problem.

Summary