Quest Engineering 1800 Instructions Manual
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7Figure 2. Output Jack ConnectionsD. Output JacksAll output jacks use a 3.5 mm stereoplug. (See Figure 2) The followingdescribes each output function:PRINT - Pressing the PRINT buttoncauses serial ASCII datato be transmitted from theprint jack at appropriateRS-232 levels. This datamay be sent to a serialprinter or a computer.The baud rate isdetermined by two switcheslocated in the batterycompartment. (See Figure4, Battery CompartmentInternal Switches, forswitch settings).DC - The Sound Pressure Level (SPL) over the 60 dB range selected islinearly represented by a 0 to 1 volt DC output. Zero volts isequal to the bottom of the range and 1 volt is equal to full scale.This output is primarily provided for connecting to a 0 to 1 voltinput chart recorder or data acquisition device. (See IV. D.,Chart Recording and Figure 8, Chart Recording of SPL)AC - This jack furnishes an amplified SPL, (either weighted orunweighted), depending on the WEIGHTING switch setting. The fullspan of 60 dB is represented between 3.16 millivolts and 3.16 voltsRMS.DATA - When the Model 1800 is in the RUN mode, an SPL reading will beserially transmitted through the DATA jack at a rate of 16 timesper second. To make use of this function, the meter range switchmust be set in one of its two highest positions.The data is an 8-bit signal proportional to the integrated soundlevel for the last 1/16 second. The signal is normally at +6.5volts. If the meter is in the RUN mode, data is sent as in Figure3. Signal description is as follows:8Figure 3. Data Jack FormatThe signal goes to -6.5 volts every 0.55 msec.If the bit is a 0 it will return to plus after 0.1 msec.If the bit is a 1 it will return plus after 0.45 msec.The signal is sent least significant bit first.The resolution is 3/8 dB.All 0's = 30 dB if the meter is set to the 60 - 120 dB range.50 dB if the meter is set to the 80 - 140 dB range.All 1's = 30 dB + 95.6 dB when set to the 60 - 120 dB range.50 dB + 95.6 dB when set to the 80 - 140 dB range.The example shown in Figure 3 is 10101100 binary = 172 decimal.The level is (172 x 3/8) + 50 = 114.5 dB when on the 80 - 140 dB range.E .E x t e r n a lF i l t e rConnectorThe 30 pinconnectoro n t h ebottom ofthe meteris usedf o rconnecting either the Model OB-300 combination 1/3 - 1/1 Octave Filter Set orthe OB-100 Octave Filter Set. Refer to section XIII for details regardingthis connector.F. Internal SwitchesThere is an internal switch located in the battery compartment that isaccessible to the user. (Refer to Figure 4.)Mic. Polarization - The small ON/OFF switch on the right-hand side operatesthe 200 volt microphone polarization which is necessaryfor condenser-type microphones.Baud Rate - Actuators 1 and 2 of the dip switch, located through thehole in the lower left, control the baud rate at whichthe meter transmits data to a printer. Baud ratesavailable are 300, 600, 1200, and 2400. |
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