$15.19 – Color: Yellow, Battery: 3x 1.5V LR Button, Resolution: 0.01 pH, Product Size: 6.10x 1.19x 0.59 inches, Measurement range: 0 to 14.0 PH, Accuracy: ± 0.01 PH Value, Temperature: 0 ~60 ℃ (32 ~140 ℉).
I have checked all old coupons and price is $15.19 for 0-14.0 PH Meter Tester Pen (in Banggood). Just check coupons out (with price alert and history). Best price?
Latest price update (UTC time):
Banggood ($15.19)
Banggood warehouse is located in China. Is it good price? Well, this price is higher than average price ($7.66) Only one coupon available!
Link: Banggood product page
Price without coupon: $15.99
1. ($15.19): BGMAI666
just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): BGcb9339, BGGines, BGTools8
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Do you need price history chart (for all/most countries) for 0-14.0 PH Meter Tester Pen? There we go. The lowest price was: $5.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).