HOW IT WORKS
LIQUID When there is clear liquid in the gap, a strong echo is received, and the Meter reads zero.	SLURRY As solids enter the gap, some of the sonic energy is absorbed by the particles, and the Meter starts to read percent solids concentration.

For the dual transducer design, the Reflector is replaced by a second transducer. One transducer transmits & the other receives the signal. The ultrasonic pulse passes only once across the gap instead of twice.
Large pipe diameters & thicker slurries and sludges use the dual transducer design because the sonic attenuation is sufficiently high to absorb most of the signal in a single pass.

MODEL 502-IL PIPING
Install a gate valve before & after the pickup head.  The flanged spoolpiece must be filled with water to calibrate Zero. If flow can not be shut off during calibration & flushing, install a bypass as shown.

 USES Series 502 Meters measure percent suspended solids (%S.S.) in sewage sludges and industrial slurries generally within the range 0.1% to 15.0% solids by weight. The exact range of the Meter depends upon the sonic attenuation of the particular sludge plus the length of the sound path. Turbidimeter applications where the solids concentration is less than 0.1% S.S. (1000 PPM) are not recommended since there are not enough particles present in the sound path to give sufficient sonic attenuation. No charge testing, and engineering assistance, is available from Markland. Applications for the Model 502-IL include shutting off a desludge pump when the sludge gets too thin, or continuously monitoring the solids flowing in a pipeline (%S.S. x Flow Rate = Solids Mass Flow). The Model 502-TP is used in open top tanks to measure concentration at various elevations, and is useful in Clarifiers to turn ON a desludge pump when the rising sludge blanket contacts the probe. Ultrasonic S.S. Meters can not be used where air or gas bubbles are present in the slurry.

INTELLIGENT MICROCONTROLLER The microcontroller continuously fires the ultrasonic transducer & interprets the received echo. Based upon its calibration parameters, the Series 502 calculates the %S.S. which it displays on the LCD. Sufficient damping is automatically included to create a smoothed output for process control (see "Automatic Dynamic Damping"). The Meter's algorithm includes error traps to prevent improper calibration and Relay settings, and these errors are displayed on the LCD for the Operator to take corrective action.  Markland's  advanced  self-diagnostic program continuously monitors the Meter's operation looking for malfunctions such as broken wires, improper voltage, etc.. If a major malfunction is detected, the Meter shuts itself down, de-energizes the Relays, and indicates the fault condition on the LCD. The 4-20 ma output can be set to default to zero ma when a major error is encountered, thus signaling to a central computer that something is wrong. Normal operation automatically resumes when a fault condition is corrected.

PUSHBUTTON CALIBRATION Series 502 Meters incorporate a simplified calibration procedure with the microcontroller doing most of the work. The technique is to calibrate zero in water, and then calibrate in a known concentration. The calibrated Meter will give linear  readings between these two settings. With the pickup head filled with water, you simply push a button and the zero is calibrated automatically. To complete the calibration, the pickup head is filled with a known concentration, and this known %S.S. value is entered through the membrane switch. If a sample has been withdrawn for analysis, and the actual concentration is not known until a lab test result is received, the Meter holds a partial calibration and waits for the actual concentration to be entered later. Calibration parameters are locked into EEPROM memory, and are permanently retained even during extended power failures. Backup batteries are not required.

AUTOMATIC DYNAMIC DAMPING Non-homogeneous materials such as sewage sludge, require output damping to prevent widely fluctuating readings which would  not  be  useable for process control.  However, homogeneous slurries such as Kaolin clay require very little damping. This meter uses a running average of many readings to smooth the output. As the difference between instantaneous readings increases (indicating a widely fluctuating signal from a nonhomogeneous material) the number of readings used in the running average is increased to damp out the fluctuations. Loss of response time is minimal since the meter takes over a thousand readings every second. When used in slurries which can vary from lumpy to smooth, automatic dynamic damping is useful to prevent unwanted wide swings in the Meter output.

ADVANCED SELF-DIAGNOSTICS Markland's advanced self-diagnostics assist the user in three ways:

1. Pressing the "Self-Diagnostic" key on the front panel calls in an instrument check which is displayed on the LCD.
2. Markland's engineering department can be contacted at Fax (416) 244-2287 to assist with stubborn field problems.
3. For more complex site-specific process problems that require a history, Markland will supply our unique self-diagnostic memory module that plugs into the Meter to record the Meter's function over time. When the module is returned, Markland can run your Meter at the factory to diagnose difficult site problems and recommend solutions.

There is No Charge for this engineering support. Markland instrumentation is carefully designed and manufactured to function in all industrial environments. If site problems develop, our advanced diagnostics will help resolve the difficulties quickly.

SET-POINT RELAYS Two independently adjustable set-point Relays (High & Low) are standard. In order to ignore short term transients, the %S.S. must exceed the set point for 30 seconds continuously, before the Relay energizes. Similarly, there is a 10 second delay which also must be continuous before the Relay will de-energize. Set-points are entered through the front panel membrane switch and are locked into EEPROM memory, which indefinitely retains the set-point, even during extended power failure, without requiring backup batteries. The LCD displays the current set-points, which are easily changed using the membrane switch.

OTHER MARKLAND SYSTEMS Markland's SLUDGE GUN^® portable sludge level detector is a valuable operating tool for manual sludge bed detection.
Markland fixed installation Series 602 sludge blanket level controls can fully automate the desludge process.  Markland
DUCKBILL^® wastewater Samplers operate without mechanical moving parts for reduced maintenance and high reliability.

SPECIFICATIONS
Range	0.1% (1000 mg/L) to 15% (150,000 mg/L) approximate. We have measured some materials up to 80%SS. Exact range varies in different materials due to variation in sonic attenuation. Contact factory for engineering assistance or NO CHARGE testing of your particular material.
Accuracy	± 1000 mg/L to 5% of full scale (depends on sonic attenuation of particular material)
Linearity	Varies in different materials. Maximum non-linearity at mid-range is usually within of 5% of full scale reading
Power	110/120 VAC, 220/240 VAC, 50/60 Hz (advise with order). 15 watts
Temperature	Liquid: 1°C to 45°C     Controller: 20°C to 50°C
Pressure	60 p.s.i.g. (4bar) 400 kpa
Outputs	· Liquid Crystal Display (LCD) 2x20 Digit Alphanumeric · 4 - 20 ma output signal, linear with %S.S. · Two DPDT, 5 Amp Relays, independently adjustable set-points · RS - 232 Serial Port · RS - 485 Serial Port (Optional)
Calibration	Pushbutton Automatic in water (zero) and in known %S.S. concentration
Damping	Automatic Variable Dynamic Damping
Response Time	30 sec. to 1 min. (max.) depending on homogeneity of slurry
Cable(s)	15 metres (50 feet) coaxial cable pigtail(s)
Enclosure	NEMA-4X (IP-67) Width 343mm (13 1/2")   ·   Height 229mm (9")   ·   Depth 200 mm (7 7/8")
Dimensions & Materials	MODEL 502-IL MODEL 502-TP Flanged steel spoolpiece pickup head, overall length 458mm (18 inches). Flange type and pipe diameter to suit pipeline PVC probe cage head with stainless steel trim, 150 mm (6 in.) offset from vertical mast. 1 inch Sch. 80 pipe mast x 4 metres (12 feet) long supplied with two stainless steel mounting clamps.
Approvals

48 SHAFT ROAD, REXDALE (TORONTO), ONTARIO, CANADA   M9W 4M2
Phone: (416) 244-4980		Fax: (416) 244-2287
E-mail: markland@sludgecontrols.com     Website: www.sludgecontrols.com