Polarographic Dissolved Oxygen Sensor The analog Dissolved Oxygen Sensor, also known as a membrane-covered dissolved oxygen electrode or polarographic oxygen electrode, is an essential tool for measuring dissolved oxygen (DO) levels in various applications. This article provides an overview of the analog dissolved oxygen sensor, including its structure, working principle, applications, and usage considerations. The analog dissolved oxygen sensor consists of a silver anode and a platinum cathode embedded in an insulating material. The silver anode is shaped like a ring, and the platinum cathode is located at the center of the ring. The electrode surface is covered with a membrane, and the space between the electrode and the membrane is filled with potassium chloride solution as the electrolyte. When a polarizing voltage is applied between the two electrodes of the oxygen electrode, dissolved oxygen that passes through the membrane into the potassium chloride solution undergoes a reduction reaction at the platinum cathode, while the silver anode undergoes an oxidation reaction. This process generates an electrolytic current between the electrodes. The magnitude of the electrolytic current is limited by the diffusion rate of oxygen. This electrolytic current, which is limited by the oxygen diffusion rate, is called the diffusion current. Under constant polarizing voltage and temperature conditions, the magnitude of the diffusion current has a good linear relationship with the oxygen concentration in the measured solution, which serves as the basis for the quantitative determination of dissolved oxygen. Â The analog dissolved oxygen sensor is widely used in various industries due to its low cost and high applicability. It can be applied to: To ensure accurate measurements, it is important to be aware of the following usage considerations for the analog dissolved oxygen sensor: Analog dissolved oxygen sensor is a cost-effective and versatile tool for measuring dissolved oxygen levels in various applications. By understanding its structure, working principle, applications, and usage considerations, users can ensure accurate measurements and optimal performance. If you are interested in learning more about the analog dissolved oxygen sensor or need technical support, please feel free to contact us. Analog Dissolved Oxygen Sensor,Dissolved Oxygen Electrode,Polarographic Oxygen Electrode Suzhou Delfino Environmental Technology Co., Ltd. , https://www.daruifuno.comOverview
Structure and Working Principle
Applications
Usage Considerations
Conclusion
Imported iron ore prices plummeted
In the second quarter, the iron ore market is facing a significant challenge: high inventory levels and limited demand growth for the rest of the year. Once a strong performer two years ago, iron ore prices have now experienced a sharp decline, reminiscent of a "cliff drop."
According to the latest report from Goldman Sachs, China's record-high iron ore inventories and structural oversupply from overseas are expected to push prices below $100 per ton in 2015. In fact, the decline has already started this year, with prices dropping from over $120 per ton to around $103 as of early May — a new low since mid-2012.
Port inventory data shows that by May 9, major Chinese ports held 111 million tons of iron ore, up 0.54% from the previous period and significantly higher than the 75.2 million tons recorded a year earlier. Guotai Junan analyst Liu Qiuping noted that port stocks have remained consistently high at around 100 million tons this year, with market expectations accounting for about 30% of the reason.
Despite the record inventory levels, iron ore prices have taken a different trajectory. The First Financial Daily reported that prices have been falling since the start of the year, and the current level is not only a new low but also reflects weak demand across the supply chain.
Steel mills, traders, and downstream users are all being cautious in their purchasing decisions. A large steel plant in North China revealed that its inventory stands at about 600,000 tons, with an additional 800,000 tons in floating stock, enough to last roughly 10 days. Some plants have even reduced their stock to as little as seven days.
A steel mill in Shanxi confirmed that it mainly purchases iron ore on a spot basis, keeping stock for about a week, with some periods down to three days when prices are low. This approach has also been echoed by traders, who report that sales have slowed compared to previous years.
One trader in East China said that while deals used to involve 10,000–20,000 tons, now they're only handling a few thousand. With ample supply from northern ports, competition is fierce, and shipments are struggling.
Even those with access to mines are feeling the pressure. While last year’s mining operations still generated small profits, this year’s price drops have wiped out margins. Some non-mainstream minerals have also seen sharp declines, leaving traders with no profit.
Liu Qiuping explained that increased shipments from major miners, combined with cautious procurement by domestic steel mills, have led to a weak market. Many buyers are delaying purchases or avoiding high-priced ores, which has kept prices under downward pressure.
The sharp drop in iron ore prices is also linked to trade financing risks. The traditional model involves steel mills or traders using letters of credit issued by foreign banks, often for 3–6 months. After paying a deposit of 15–30%, the bank pays the miner, and the ore is delivered later, allowing for short-term financing.
However, the China Banking Regulatory Commission recently issued a notice to monitor the risks of iron ore trade, requiring regional banking regulators to submit reports on risk statistics. As a result, many domestic banks have raised letter of credit deposit requirements to 30–50%.
Some pre-existing letters of credit are set to expire in May, leading to increased selling pressure as traders look to repatriate funds. Media reports indicate that the deposit ratio for iron ore L/Cs has risen sharply, with many banks suspending new issuances. As a result, many traders have stopped importing and are now selling iron ore to free up capital.
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