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Models 1220 & 1223 - Multipoint Combustibles System
How far can a sensor be located from the channel module? The maximum distance from the channel module to the sensor depends upon the amount of loop resistance the wire adds. A larger-diameter wire will have a lower resistance and will allow longer cable runs. For a single-sensor applications, the maximum total loop resistance is 35 W. For a dual-sensor application, the maximum loop resistance for each sensor is 20 W. This means there can be no more than 17.5 W on each of the black and red wires (sensors have a black and a red lead) for single-sensor applications, and no more than 10 W on each of the wires for dual-sensor applications. The following table lists the maximum distance that a sensor may be placed from the control module based upon the gauge of the wire. This data was generated based upon the use of stranded copper wire at ambient temperatures not exceeding 50 degrees C. The values may be different depending upon the manufacturer of the wire and the ambient temperature, so we recommend you re-calculate the values based upon your particular requirements. This data is for straight runs (no splicing). If your application requires splicing or intermediary connections, you should take the junction resistances into account.
Top of page What is the recommended gauge size and number of conductors for the interconnect wiring? The recommended gauge size is summarized in the table above and depends upon the distance between the channel module and the sensor. For reliability and durability, we recommend the wire not be smaller in diameter than 22 gauge. Top of page What are the electrical ratings of the relays in the unit? The relays are presently rated at 5A / 250 VAC (resistive). Top of page What does the "Sensor Gauge" on the channel module measure? The "Sensor Gauge" measures the sensitivity of the sensor. This is the amount of milli-volts that the sensor outputs for each percent LEL of the gas being measured. Typically, as the sensor ages, wears, or becomes dirty the sensitivity will decrease (fewer milli-volts will be generated per percent LEL). A typical sensor will output approximately 3mV per LEL, but this varies from sensor to sensor and changes with the gas being measured. Because of this variance, the scale on the model 1220 is adjustable and is referenced to a calibrated sensitivity. During the first calibration, you may set the sensitivity gauge to full-scale by using the left and right arrows to adjust the gauge to 100 %. After setting the gauge to 100%, the present sensitivity becomes the reference for future gauge displays. With each subsequent calibration, the sensitivity gauge will adjust to show how much the sensitivity has dropped since the first calibration. Top of page How does the two sensor option work? Are they both continuous? Signal averaging? Sequenced? The two sensor option is activated by inserting a second "Sensor PCB" into the instrument. The two sensors are monitored by the 1220 on a continuous basis. The signals are NOT averaged. There is only one set of alarm relays and setpoints. If either of the sensors rises above an alarm setpoint, that alarm will be activated. Even if one sensor triggers the caution alarm, the other sensor may still trigger the high alarm. Top of page How often should the system be calibrated? The frequency of required calibration will vary with individual accuracy requirements and sensor drift. Top of page What are the recommended calibration gases? Teledyne recommends that for best accuracy the user calibrate at approximately 80% of scale of the specific gas of interest (i.e. methane, propane, etc). Top of page Does Teledyne offer a calibration kit? Not at this time. Calibration gas mixtures can be readily obtained from vendors such as Matheson or Scott Specialty Gases. Top of page What gases poison the sensor? Sulfur and silicon containing gases or compounds can degrade the performance of the sensor. Top of page Where do I mount the sensors? The sensors' mounting should be evaluated by the safety officer responsible for the site in lieu of the requirements for hazardous area use promulgated by the Instrument Society of America, or other regionally relevant regulations. Top of page Can I monitor combustible gas in non-air backgrounds? Yes, but there must be a minimum of 1% O2 present at all times. Top of page What is the principle of operation of a Flame Ionization Detector? A flame-ionization detector (FID) is the most popular detector for the analysis of hydrocarbons due to its high sensitivity, wide linear dynamic range, low dead volume, and responsiveness to trace levels of almost all organic compounds. An FID adds hydrogen to the column effluent and passes the mixture through a jet where it is mixed with entrained air and burned. The ionized gas (charged particles and electrons produced during combustion) passes through a cylindrical electrode. A voltage applied across the jet and cylindrical electrode sets up a current in the ionized particles. An electrometer monitors this current to drive a measure of the component concentration. An ignitor coil and flame out sensor are placed above the jet to re-ignite the flame should it become extinguished. The entire system is placed inside a chimney to avoid drafts and condensation of water droplets resulting from the combustion process. The response of the FID is proportional to the number of CH12 groups that enter the flame. The response to the carbons attached to the hydroxyl groups and amine groups is lower. There is no response to fully oxidized carbons such as carbonyl or carboxyl, and to ether groups. The detector is insensitive to moisture and to permanent gases. Modest changes in flow, pressure, or temperature have only a small effect on the response. The quality of both the carrier gas and hydrogen support gas is more critical than that of the flame support air. The presence of organic substances in any of theses gases will increase the detector noise and the minimum detectable limit and, therefore, decrease the dynamic range. The design of the jet is important so that the flow does not convolute and cause a turbulent flame. Top of page We are installing a 1223B with dual sensors per channel for an H2 plant. Is it possible to simulate a signal check for each channel module? If so, please advise the signal type and its equivalent range to 0-100% LEL. Also, please advise if we can monitor two locations at a time with the dual sensors per channel. Download our recommendations to simulate the signal from a combustibles sensor, 0-100% LEL. You can monitor two locations at the same time with the dual sensors analyzer. The single control unit will indicate "with relay alarm contacts and LEDs" that an alarm condition has occurred at one or both locations, but will not differentiate between the two locations. Top of page I want to calibrate with 1.25% Methane to read 0-100% LEL for propane. What value should be entered during span calibration? If calibrating with span gas of 1.25% methane, span the instrument to 40% LEL to read 0-100% LEL propane, Refer to formula and cal factor list in manual: CH4 span gas x Calibration factor = % LEL (1.25 x 32 = 40). Top of page We are currently using a 1.25% Methane standard to calibrate our handheld gas detectors. I would like to also use this standard to calibrate our Teledyne LELs. Can you tell me how I need to go about making the 1.25% Methane standard equivelent to the 1% Propane standard I have been using? The response factor for propane is 1.42 vs 1.00 for methane. (This comes from our Combustible manuals). Several piecesof literature sites different values from (1.42 to 1.75) 0-100% lel methane = 0 - 5% methane 0-100% lel propane = 0 - 2.2% propane However: because propane responds differently, we must determine the methane to propane relationship by concentration since that is what the customer is asking for, so: Our literature says: Calibrate the unit with methane for 0-5% = 0-100% LEL, so they cal with 1.25% methane, then introduce 1 % propane std and calculate as follows: (meter reading as methane eq/1.42 response factor for propane) = 1% propane which is 45% LEL as propane [(1%/2.2%) = 45.4% LEL] and 45.4% x 0.88 factor = 40% LEL as propane equivalents which is equal to 1.25% methane at 25% methane LEL equivalents. the meter should read 1.42% methane equivalents for 1% propane. however the customers gas std is only 1.25% methane (25% LEL) So: What % of 1.42% gives 1.25% methane equivalent, i.e., X% times 1.42 = 1.25% methane X = 0.88 factor. So with 1% propane in the unit, they need to multiply the reading by 0.88 to get the equivalent 1.25% methane reading. 0.88 x 1.42% reading for 1% propane = 1.25% CH4. This assumes the true response factor is 1.42 NOTE: You cannot make 1% propane = 1.25% methane unless you multiply the reading of 1.42% by this factor (0.88). Top of page What are the failure codes for this unit?
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Document Control & Training (password) e-mail us: ask_tai@teledyne.com Copyright © 2007 Teledyne Technologies Incorporated. All rights reserved. Teledyne Analytical Instruments • 16830 Chestnut St • City of Industry, CA 91748 • USA |
