TMQ-34 Meteorological Measuring Set

Sensor

The main component is a multi-function weather sensor that can be either hand held or attached to a standard american camera tripod (1/4-20 thread). It connects to the digital display unit with a short cable (but maybe a longer cable could be used). The sensor contains a magnetic compass so the wind direction is reported on the Display in magnetic bearing. This way it does not matter how the sensor is pointed, just held still. Directly under the center of the label there's a metal tab which when removed allows the sensor to be taken apart. There's a wind direction scale on top of the wind speed drum with angles marked every 45 degrees, but since the drum turns in the wind it's not much use? If the wind speed drum is spun manually it keeps on spinning for a long time indicting that the bearings are very good and that the minimum wind speed that is detectable may be low. The cable is attached to the sensor and has a Bendix H9530-12 MS27473E10B13P connector, but only 6 pins are installed. The sensor outputs are analog signals in the 0.1 to 5 volt range.

The sensor connector is wired as follows:

A. Ground
B. + 10 to +15 V @ 10 ma
C. Wind Speed 0 to 100 mph (0.1 to 5 V)
D. Wind Direction 0 to 360 deg magnetic (0.1 to 5 V)
E. Temp -58 F (-50 C) to +131 F (55 C) (0.1 to 5 V)
F. Relative Humidity 0 to 100% (0.1 to 5 V)

Long Sensor Cable

When a long cable is used with JTG06RE 10-13P and JTG06RE 10-13S connectors there will be a DC offset caused by the cable resistance. When using an indoor voltmeter to read the sensor to get around this an extra wire can be run from the sensor end ground terminal (pin A) back to the indoor meter ground terminal. This way the DC voltage drop in the ground lead will not be part of the voltage measurement. It's too bad that the stock TMQ-34 didn't use this method to support extension cables. It may be possible to modify the TMQ-34 to support this pseudo Kelvin measurement method. Sure would be nice to have a schematic diagram for it.

Display

Marked: Computer, Assy, p/o AN/TMQ-34, Des Act: 10241, Mfr: 10241, Part No. WD8500-22, Contract No. F04606-86-C-0630
The display unit has a selector switch to determine what the alpha numeric LED display shows:

Wind Avg Dir (deg)
Wind Avg Sp (Knots)
Wind Dir-Pk Sp-Time (Deg-Knots-Min)
Temperature (deg C)
Dew Point (Deg C)
Baro Pressure (Millibars)
3 Hr Baro Press Change
Min Temp-Time (deg C-min) &Max Temp-Time (deg C-min)
Test -> all pixels on in sequence then PASS or FAIL.

On one side of the display box there's a temperature conversion nomagram covering the range -50C/-60F to +50C/+120F, it's not clear if a user attached a stnecil or if this is a stock thing.

The display has two major parts:

Main Box

This has the battery compartment and the barometric pressure sensor that has a tube going through a desiccant to the outside atmosphere. The "Power" circuit breaker and the connector for the hand held sensor.

Display Panel

This has a circuit board attached and has all the electronics for the weather station (except for the baro pres specific stuff). Uses a 12 to 5 Volt DC-DC converter and a couple of crystals (1.048576 & 3.68640 MHz).

Included with the set is a Lufkin 066D six foot folding wood ruler. Maybe this is used to set the height of the sensor above the ground.
Another possible use would be to measure the depth of snow.

There is a "GAGE, PRECIPITION ML-614/G". (spelling should be gauge & precipitation). Calibrated to both 2 inches and 50 mm. The bottom end has a 0.22" diameter hole about 0.7" deep to hold it, but what does that fit in the kit? Also there is another part stowed inside the rain gage, but it's purpose is not clear. Ans: I have parts of 2 different style gauges that are not compatible.

"Kit, Sensor Test" that contains two parts:
One is a hollow plastic cone with a metal rod coming out the pointed end. Use unknown
The other is a plastic clip that can be slipped onto the sensor wind direction or speed rotors and when the sensor is held with it's axis parallel to the ground the rotor should turn because of the weight of the clip. If the rotor does not turn there's too much friction.

The Philips screw driver is needed to open the battery compartment.

The handle with a 1/4-20 screw on top fits the bottom of the sensor for hand held use.

The neck strap clips onto the display so no hands are needed for holding the display. One hand to hold the sensor and one hand to set the display switch and press the measure button.

Operation

Instruction Sheet

Preparation: Remove assembly and place on flat surface. Verify PWR circuit is off (pulled out). Remove top of assembly and insert Ni-Cad battery. Replace cover. Connect sensor assembly to computer assembly.

Operation: Set PWR circuit breaker to 'ON' position (pushed in). Set SENSOR FUNCTION switch to position 9 (test). Within 10 seconds of initial turn-on, depress and release READ/TEST button and observe the word WAIT (2 seconds) on the panel. Wait at least 10 seconds, depress and release the Read/Test button and observe: 1) All pixels on the first and third segments illuminate and then disappear; then the second and fourth segments illuminate and disappear. (2) The display panel indicates PASS three seconds after the READ/TEST is depressed. This indicates the unit is ready for normal operation. If PASS is not displayed, a failure code will indicate a malfunction.

Wind Direction: Set sensor function switch to position 1. Depress and release READ/TEST switch.

Wind Speed: Set function switch to position 2. Depress and release READ/TEST switch.

Temperature: Function position 4 (READ/TEST switch).

Dew Point: Function position 5.

Average Wind Direction: Function position 1. Wait three minutes and depress READ/TEST button. Average Wind Speed: Function position 2. Wait three minutes and depress READ/TEST button.

Average Wind Speed: Function position 2. Wait three minutes and press READ/TEST button.

Wind Direction/Peak Speed: Position 3.

Barometric Pressure: Function position 5. Depress READ/TEST button.

Turn-Off: Set PWR circuit breaker to off (pulled out). Remove battery. Disconnect sensor assembly.

When the battery is installed the barometric pressure sensor starts logging data so that when the 3 hour baro pressure change test is run there will be something to compare aginst.

To get the display to turn on the Read/Test Hold button needs to be pressed and released.
The POWER button appears to be a circuit breaker and it's normal position is down. If it pops up there may be a problem. You can manually lift the button to turn off the unit.

22 April 2005 - my Loran-C receivers both lost lock and the sferics lamp on the Loran-C filter has been flashing, so I'm expecting a thunder storm. So started logging the baro pressure.

PDT pm	Baro Pres mb	3 hr delta Baro Pres	Comment
5:07	997.6		installed battery
6:24	972.5
6:44	980.2
6:47	980.2		Thunder
6:55	980.2		Rain
7:07	980.7		"
7:37	980.7		"
8:31	980.6		"
9:14	981.0	1.7	"

9:35 pm PDT measured inside:

Wind Avg Dir (deg) = 226.2
Wind Avg Sp (Knots) = 21
Wind Dir-Pk Sp-Time (Deg-Knots-Min) = 128.1 2.2 0.
Temperature (deg C) = 27.4 (BATT CC#2 HH#2) The strange display caused by holding the button down.
Dew Point (Deg C) = 18.9
Baro Pressure (Millibars) = 981.3
3 Hr Baro Press Change = 1.3
Min Temp-Time (deg C-min) & Max Temp-Time (deg C-min)= 27.4 2 28.4 2
= FAIL if battery is low. PASS if battery is OK.

Note if the battery is changed quiclkey the 3 hour baro pressure is not reset.

Test results depend on battery condition & how the button is pressed, HH#3, HH#4, 502 with weak battery, and 250.4, .6, 0. with good battery.

Sensor on Mast

In the photo on the left the sensor is mounted on a mast which seems to be suported by 3 or 4 white tape ribbons and the computer is on a stack of transit cases. The photo caption on the FAS web page is:
"Airman First Class Eric Andrews takes an observation with the TMQ-34 Tactical Meteorological Sensor."

How is the sensor attached to the mast, does it just plug in?

Barometric Sensor

The digtial barometer was made by Atmospheric Instrumenttin Research (A.I.R.) which is now part of Vaisala. Model number on the sensor is AIR-DB-2ATS1. The code in the uP is patented by A.I.R.

Patents held by A.I.R.:
Class 73 Measuring & Testing
    335 - Hygrometer
    170 - radiosonde
Class 342 Communiction: Directive Radio Wave SYSTEMS & Devices (e.g. RADAR, Radio Navigation
    357.12 - GPS receiver signal processing
5345821 Relative humidity sensing apparatus Sep 13, 1994 73/335.04; 324/664; 422/98
5347285 Method and apparatus for tracking the position and velocity of airborne instrumentation Sep 13, 1994 342/357.12; 342/352; 342/463
4907449 Meteorological data encoder for measuring atmospheric conditions March 13, 1990 73/170.28; 73/724; 374/170

DC Power

Battery

The display box holds a BA-5557/U or BB-557/U NSN 6140-01-071-5070 battery.
The BB-557 is a Ni-Cad battery rated at 0.45 amp hours. The battery label says to charge it at 100 ma for 6 hours.
Note the BB-557/U is a smaller version of the BA-5590. It has the same socket as a BB-390 or BB-590 and the socket is wired the same.

The display has the battery plug pin 1 connected to pin 2, and it has pin 4 connected to pin 5. This puts the two "12 Volt" batteries in parallel. So the weather station operating voltage appears to be 10 to 15 VDC.

The design of the display battery compartment is such that a BA-5590 will NOT fit when the cover is removed. That's because the BB-557 is 4 3/16" long and the BA-5590 is 4 3/8" long. If they would have made the "notch" in the display box a little longer you could use a BA-5590 family battery when the cover was removed.

Charger

The Battery charger plug has a jumper between pins 2 and 4 and so is charging the two halves in series with pin 3 being the negative terminal and 5 being the positive terminal. This way you can not charge a primary (BA-5557) battery. There are two spare 250 v, 1/4A fuses inside the box.

The power transformer can be strapped for either 110 or 220 VAC input. Both the input and the output are fused. There are a couple of threaded inserts that would allow this charger to be mounted to something, but what is not clear. Maybe the charger is also used in other applications. The Green LED BAT CUR indicator only comes on when current is being supplied to the battery. So if a BA-5590 is connected there is no charge current (no pin 3 connection in the battery) and no LED light.

The circuit appears to be a transformer fed bridge rectifier feeding a single pass transistor. 44 is the open circuit output voltage. If the internal resistance was 425 Ohms then when a 27 Volt battery was connected the current would be about 40 ma. For a dead battery (20 V) the current would be about 60 ma. This may not be correct, but is close to the recomended 100 ma charge current for the BB-557/U.

The trickle charge current is about 40 ma into a string of 20 Ni-MH cells that are fully charged. This charger may be able to charge the 5590BA Battery Adapter.