Sierra Wireless DART 300 Installation Considerations, Environment, Temperature and Auto Shutdown

11. Installation Considerations

The DART 300 CDPD modem is designed for stationary applications, not in-vehicle installations. Due to the varied applications of the DART modem, there is no single correct way to install the product. What follows are guidelines for making appropriate installation decisions.

Use the previous section on Device Attachment for information on making the actual connections to the antenna, serial data, and power.

11.1. Environment

The standalone DART 300 is ruggedly constructed. However, it is not waterproof, so do not locate the modem where it can get wet. Also, refer to the humidity specification in Section 14.3 below. If installing the DART 300 in a wet environment, enclose it in a proper National Electrical Manufacturer’s Association (NEMA) enclosure.

11.1.1.Temperature and Auto Shutdown

The modem has a temperature sensor at the radio within the unit. If the radio reaches 75°C the modem will shutdown automatically to prevent the radio from deviating from specifications. When the modem has cooled, it will reset as though there had been a power-cycle.

Always install the unit where there is adequate ventilation to prevent possible overheating. If the modem is transmitting on a high duty cycle, it can become quite hot inside the case. The section below includes suggestions on allowable duty cycle for given ambient temperatures.

11.1.2.Temperature vs. Duty Cycle

The temperature within the modem is highly dependent on the duty cycle of the transmitter. If the modem is transmitting in short bursts (3 seconds or less) at intervals of a minute or more (~5%), there should be little problem within the nominal temperature range of the modem (-30 to +55°C). For higher duty cycle operation, consult the chart below.

	120
	100
(minutes)	80
	60
Time	40
	20
	0
	25	30	35	40	45	50	55

Ambient Temperature (C)

5%

10%

25%

50% 100%

This chart shows the time taken (y axis) to reach the modem’s Auto Shutdown at a given ambient temperature (x axis) for each of the transmitter duty cycles shown in the legend. A 5% duty cycle is sustainable at all temperatures. Higher duty cycles can be sustained for periods less than two hours.

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